diff --git a/src/backend/thread_bookgrabber.py b/src/backend/thread_bookgrabber.py
index efae485..71752ba 100644
--- a/src/backend/thread_bookgrabber.py
+++ b/src/backend/thread_bookgrabber.py
@@ -1,5 +1,3 @@
-import sqlite3
-
 from PyQt6.QtCore import QThread
 from PyQt6.QtCore import pyqtSignal as Signal
 from src.backend import Database
@@ -25,19 +23,20 @@ class BookGrabber(QThread):
     updateSignal = Signal(int, int)
     done = Signal()
 
-    def __init__(self, appnr: int):
+    def __init__(self):
         super(BookGrabber, self).__init__(parent=None)
         self.is_Running = True
         logger.info("Starting worker thread")
-        self.data = None
+        self.data = []
         self.app_id = None
         self.prof_id = None
         self.mode = None
         self.book_id = None
         self.use_any = False
         self.use_exact = False
-        self.appnr = appnr
+        self.app_id = None
         self.tstate = (self.app_id, self.prof_id, self.mode, self.data)
+        self.request = WebRequest()
 
     def add_values(
         self, app_id: int, prof_id: int, mode: str, data, any_book=False, exact=False
@@ -45,27 +44,26 @@ class BookGrabber(QThread):
         self.app_id = app_id
         self.prof_id = prof_id
         self.mode = mode
-        self.data = data
+        self.data: list[str] = data
         self.use_any = any_book
         self.use_exact = exact
         logger.info(f"Working on {len(self.data)} entries")
         self.tstate = (self.app_id, self.prof_id, self.mode, self.data)
         logger.debug("State: " + str(self.tstate))
-        # print(self.tstate)
+        self.request.set_apparat(self.app_id)
+        # logger.debug(self.tstate)
 
     def run(self):
         self.db = Database()
         item = 0
         iterdata = self.data
-        # print(iterdata)
-        if self.prof_id is None:
-            self.prof_id = self.db.getProfNameByApparat(self.app_id)
-        for entry in iterdata:
-            # print(entry)
-            signature = str(entry)
-            logger.info("Processing entry: " + signature)
+        # logger.debug(iterdata)
 
-            webdata = WebRequest().set_apparat(self.appnr).get_ppn(entry)
+        for entry in iterdata:
+            # logger.debug(entry)
+            logger.info("Processing entry: {}", entry)
+
+            webdata = self.request.get_ppn(entry)
             if self.use_any:
                 webdata = webdata.use_any_book
             webdata = webdata.get_data()
@@ -74,12 +72,12 @@ class BookGrabber(QThread):
                 continue
 
             bd = BibTextTransformer(self.mode)
-            print(webdata)
+            logger.debug(webdata)
             if self.mode == "ARRAY":
                 if self.use_exact:
                     bd = bd.use_signature(entry)
             bd = bd.get_data(webdata).return_data()
-            print(bd)
+            logger.debug(bd)
             if bd is None:
                 # bd = BookData
                 continue
@@ -95,19 +93,21 @@ class BookGrabber(QThread):
             logger.info("Added book to database")
             state = 0
             for result in transformer.RDS_DATA:
-                # print(result.RDS_LOCATION)
+                # logger.debug(result.RDS_LOCATION)
                 if str(self.app_id) in result.RDS_LOCATION:
                     state = 1
                     break
 
-            logger.info(f"State of {signature}: {state}")
-            print("updating availability of " + str(self.book_id) + " to " + str(state))
+            logger.info(f"State of {entry}: {state}")
+            logger.debug(
+                "updating availability of " + str(self.book_id) + " to " + str(state)
+            )
             try:
                 self.db.setAvailability(self.book_id, state)
-                print("Added book to database")
+                logger.debug("Added book to database")
             except Exception as e:
                 logger.error(f"Failed to update availability: {e}")
-                print("Failed to update availability: " + str(e))
+                logger.debug("Failed to update availability: " + str(e))
 
             # time.sleep(5)
             item += 1
@@ -135,7 +135,7 @@ class BookGrabberTest(QThread):
         self.book_id = None
         self.use_any = False
         self.use_exact = False
-        self.appnr = appnr
+        self.app_id = appnr
         self.tstate = (self.app_id, self.prof_id, self.mode, self.data)
         self.results = []
 
@@ -151,18 +151,18 @@ class BookGrabberTest(QThread):
         logger.info(f"Working on {len(self.data)} entries")
         self.tstate = (self.app_id, self.prof_id, self.mode, self.data)
         logger.debug("State: " + str(self.tstate))
-        # print(self.tstate)
+        # logger.debug(self.tstate)
 
     def run(self):
         item = 0
         iterdata = self.data
-        # print(iterdata)
+        # logger.debug(iterdata)
         for entry in iterdata:
-            # print(entry)
+            # logger.debug(entry)
             signature = str(entry)
             logger.info("Processing entry: " + signature)
 
-            webdata = WebRequest().set_apparat(self.appnr).get_ppn(entry)
+            webdata = WebRequest().set_apparat(self.app_id).get_ppn(entry)
             if self.use_any:
                 webdata = webdata.use_any_book
             webdata = webdata.get_data()
@@ -188,13 +188,13 @@ class BookGrabberTest(QThread):
             logger.info("Added book to database")
             state = 0
             for result in transformer.RDS_DATA:
-                # print(result.RDS_LOCATION)
+                # logger.debug(result.RDS_LOCATION)
                 if str(self.app_id) in result.RDS_LOCATION:
                     state = 1
                     break
 
             logger.info(f"State of {signature}: {state}")
-            # print("updating availability of " + str(self.book_id) + " to " + str(state))
+            # logger.debug("updating availability of " + str(self.book_id) + " to " + str(state))
             self.results.append(bd)
 
             # time.sleep(5)
diff --git a/src/logic/webrequest.py b/src/logic/webrequest.py
index 142d962..9c06bdb 100644
--- a/src/logic/webrequest.py
+++ b/src/logic/webrequest.py
@@ -4,7 +4,7 @@ from bs4 import BeautifulSoup
 
 # import sleep_and_retry decorator to retry requests
 from ratelimit import limits, sleep_and_retry
-
+from typing import Union, Any
 from src.logic.dataclass import BookData
 
 from src.transformers import ARRAYData, BibTeXData, COinSData, RDSData, RISData
@@ -61,14 +61,14 @@ class WebRequest:
         logger.info("Using any book")
         return self
 
-    def set_apparat(self, apparat):
+    def set_apparat(self, apparat: int):
         self.apparat = apparat
         if int(self.apparat) < 10:
             self.apparat = f"0{self.apparat}"
         logger.info(f"Set apparat to {self.apparat}")
         return self
 
-    def get_ppn(self, signature):
+    def get_ppn(self, signature: str):
         self.signature = signature
         if "+" in signature:
             signature = signature.replace("+", "%2B")
@@ -79,15 +79,15 @@ class WebRequest:
 
     @sleep_and_retry
     @limits(calls=RATE_LIMIT, period=RATE_PERIOD)
-    def search_book(self, searchterm: str):
+    def search_book(self, searchterm: str) -> str:
         response = requests.get(PPN_URL.format(searchterm), timeout=self.timeout)
         return response.text
 
-    def get_book_links(self, searchterm: str):
-        response = self.search_book(searchterm)
+    def get_book_links(self, searchterm: str) -> list[str]:
+        response: str = self.search_book(searchterm)  # type:ignore
         soup = BeautifulSoup(response, "html.parser")
         links = soup.find_all("a", class_="title getFull")
-        res = []
+        res: list[str] = []
         for link in links:
             res.append(BASE + link["href"])
         return res
@@ -102,10 +102,11 @@ class WebRequest:
             logger.error(f"Request failed: {e}")
             return None
 
-    def get_data(self):
+    def get_data(self) -> Union[list[str], None]:
         links = self.get_book_links(self.ppn)
+        logger.debug(f"Links: {links}")
         for link in links:
-            result = self.search(link)
+            result: str = self.search(link)  # type:ignore
             # in result search for class col-xs-12 rds-dl RDS_LOCATION
             # if found, return text of href
             soup = BeautifulSoup(result, "html.parser")
@@ -117,7 +118,7 @@ class WebRequest:
                     ).text.strip()
                     if self.use_any:
                         pre_tag = soup.find_all("pre")
-                        return_data = []
+                        return_data: list[str] = []
                         if pre_tag:
                             for tag in pre_tag:
                                 data = tag.text.strip()
@@ -126,7 +127,7 @@ class WebRequest:
                         else:
                             logger.error("No <pre> tag found")
                             raise ValueError("No <pre> tag found")
-                    if f"Semesterapparat-{self.apparat}" in item_location:
+                    elif f"Semesterapparat-{self.apparat}" in item_location:
                         pre_tag = soup.find_all("pre")
                         return_data = []
                         if pre_tag:
@@ -137,6 +138,13 @@ class WebRequest:
                         else:
                             logger.error("No <pre> tag found")
                             return return_data
+                    else:
+                        logger.error(
+                            f"Signature {self.signature} not found in {item_location}"
+                        )
+                        return_data = []
+
+                        return return_data
 
     def get_data_elsa(self):
         links = self.get_book_links(self.ppn)
@@ -184,7 +192,7 @@ class BibTextTransformer:
         self.signature = signature
         return self
 
-    def get_data(self, data: list):
+    def get_data(self, data: Union[list[str]] = None) -> "BibTextTransformer":
         RIS_IDENT = "TY  -"
         ARRAY_IDENT = "[kid]"
         COinS_IDENT = "ctx_ver"
@@ -217,7 +225,7 @@ class BibTextTransformer:
                     self.data = line
         return self
 
-    def return_data(self, option=None) -> BookData:
+    def return_data(self, option: Any = None) -> Union[BookData, None]:
         """Return Data to caller.
 
         Args:
@@ -239,7 +247,7 @@ class BibTextTransformer:
                 return RISData().transform(self.data)
             case "RDS":
                 return RDSData().transform(self.data).return_data(option)
-            case None:
+            case _:
                 return None
 
         # if self.mode == "ARRAY":
@@ -256,7 +264,7 @@ class BibTextTransformer:
 
 def cover(isbn):
     test_url = f"https://www.buchhandel.de/cover/{isbn}/{isbn}-cover-m.jpg"
-    # print(test_url)
+    # logger.debug(test_url)
     data = requests.get(test_url, stream=True)
     return data.content
 
@@ -266,8 +274,8 @@ def get_content(soup, css_class):
 
 
 if __name__ == "__main__":
-    # print("main")
+    # logger.debug("main")
     link = "CU 8500 K64"
     data = WebRequest(71).get_ppn(link).get_data()
     bib = BibTextTransformer("ARRAY").get_data().return_data()
-    print(bib)
+    logger.debug(bib)
diff --git a/src/logic/wordparser.py b/src/logic/wordparser.py
index 6e733c0..29d6259 100644
--- a/src/logic/wordparser.py
+++ b/src/logic/wordparser.py
@@ -67,7 +67,7 @@ class Book:
                 self.location = value.split(",")[0] if "," in value else value
                 self.publisher = value.split(",")[1] if "," in value else ""
             elif key == "Standnummer":
-                self.signature = value
+                self.signature = value.strip()
             elif key == "Interne Vermerke":
                 self.internal_notes = value
 
@@ -212,7 +212,7 @@ def elsa_word_to_csv(path):
     data = [
         row for row in df.itertuples(index=False, name=None) if row != tuples[doctype]
     ]
-    # print(data)
+    # logger.debug(data)
     return tuple_to_dict(data, doctype), doctype
 
 
diff --git a/src/transformers/transformers.py b/src/transformers/transformers.py
index 5f8aa48..765a911 100644
--- a/src/transformers/transformers.py
+++ b/src/transformers/transformers.py
@@ -7,8 +7,20 @@ from dataclasses import field as dataclass_field
 from typing import Any, List
 
 
-
 from src.logic.dataclass import BookData
+import sys
+from loguru import logger as log
+
+logger = log
+logger.remove()
+logger.add("logs/application.log", rotation="1 week", enqueue=True)
+log.add(
+    "logs/transformers.log",
+    enqueue=True,
+)
+
+# logger.add(sys.stderr, format="{time} {level} {message}", level="INFO")
+logger.add(sys.stdout)
 
 
 ###Pydatnic models
@@ -131,7 +143,7 @@ class ARRAYData:
                 return data
 
             except Exception:
-                # # print(f"ARRAYData.transform failed, {source}, {search}")
+                # # logger.debug(f"ARRAYData.transform failed, {source}, {search}")
                 logger.exception(f"ARRAYData.transform failed, no string {search}")
                 return ""
 
@@ -509,4 +521,4 @@ if __name__ == "__main__":
 
     ret = RDSData().transform(data)
     data = ret.return_data("rds_availability")
-    # print(data)
+    # logger.debug(data)
diff --git a/src/ui/userInterface.py b/src/ui/userInterface.py
index d2ad1d5..7636603 100644
--- a/src/ui/userInterface.py
+++ b/src/ui/userInterface.py
@@ -765,7 +765,7 @@ class Ui(Ui_Semesterapparat):
             # create a thread that updates the progress label after each medium
 
             # self.bookGrabber = None
-            bookGrabber = BookGrabber(self.active_apparat)
+            bookGrabber = BookGrabber()
             bookGrabber.add_values(
                 mode=mode,
                 prof_id=prof_id,