diff --git a/src/corelibs/logging_handling/log.py b/src/corelibs/logging_handling/log.py
index c1fc0cf..f679fef 100644
--- a/src/corelibs/logging_handling/log.py
+++ b/src/corelibs/logging_handling/log.py
@@ -126,6 +126,7 @@ class Log:
 
         self.log_queue: 'Queue[str] | None' = None
         self.listener: logging.handlers.QueueListener | None = None
+        self.logger: logging.Logger | None = None
 
         # setup handlers
         # NOTE if console with color is set first, some of the color formatting is set
@@ -219,6 +220,10 @@ class Log:
         """
         if self.handlers.get(handler_name):
             return False
+        if self.listener is not None or self.logger is not None:
+            raise ValueError(
+                f"Cannot add handler {handler_name}: {handler.get_name()} because logger is already running"
+            )
         # TODO: handler must be some handler type, how to check?
         self.handlers[handler_name] = handler
         return True
@@ -360,6 +365,8 @@ class Log:
             *args (object): arguments for msg
             extra: Mapping[str, object] | None: extra arguments for the formatting if needed
         """
+        if self.logger is None:
+            raise ValueError('Logger is not yet initialized')
         self.logger.log(LoggingLevel.EXCEPTION.value, msg, *args, exc_info=True, extra=extra)
 
     # MARK: break line
@@ -370,6 +377,8 @@ class Log:
         Keyword Arguments:
             info {str} -- _description_ (default: {"BREAK"})
         """
+        if self.logger is None:
+            raise ValueError('Logger is not yet initialized')
         self.logger.info("[%s] %s>", info, self.SPACER_CHAR * self.SPACER_LENGTH)
 
     # MARK: queue handling
@@ -432,13 +441,15 @@ class Log:
             self.handlers[handler_name].setLevel(log_level.name)
             return True
         except IndexError:
-            self.logger.error('Handler %s not found, cannot change log level', handler_name)
+            if self.logger:
+                self.logger.error('Handler %s not found, cannot change log level', handler_name)
             return False
         except AttributeError:
-            self.logger.error(
-                'Cannot change to log level %s for handler %s, log level invalid',
-                LoggingLevel.name, handler_name
-            )
+            if self.logger:
+                self.logger.error(
+                    'Cannot change to log level %s for handler %s, log level invalid',
+                    LoggingLevel.name, handler_name
+                )
             return False
 
     def get_log_level(self, handler_name: str) -> LoggingLevel:
diff --git a/test-run/logging_handling/log.py b/test-run/logging_handling/log.py
index 41f921c..7cb2102 100644
--- a/test-run/logging_handling/log.py
+++ b/test-run/logging_handling/log.py
@@ -23,6 +23,9 @@ def main():
             # "console_color_output_enabled": False,
         }
     )
+    if log.logger is None:
+        print("failed to start logger")
+        return
 
     log.logger.debug('[NORMAL] Debug test: %s', log.logger.name)
     log.logger.info('[NORMAL] Info test: %s', log.logger.name)
diff --git a/test-run/logging_handling/log_pool.py b/test-run/logging_handling/log_pool.py
index 963e71c..058bd61 100644
--- a/test-run/logging_handling/log_pool.py
+++ b/test-run/logging_handling/log_pool.py
@@ -10,6 +10,7 @@ import concurrent.futures
 import logging
 from pathlib import Path
 from corelibs.logging_handling.log import Log
+from corelibs.logging_handling.logging_level_handling.logging_level import LoggingLevel
 
 
 def work_function(log_name: str, worker_id: int, data: list[int]) -> int:
@@ -46,7 +47,10 @@ def main():
             "log_queue": log_queue,
         }
     )
-    log.logger.info('Pool Fork logging test')
+    if log.logger is None:
+        print("logger not yet started")
+        return
+    log.logger.debug('Pool Fork logging test')
     max_forks = 2
     data_sets = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
     with concurrent.futures.ProcessPoolExecutor(
@@ -62,9 +66,23 @@ def main():
         log.logger.info('Workders started')
 
         for future in concurrent.futures.as_completed(futures):
-            log.logger.info('Processing result: %s', future.result())
+            log.logger.warning('Processing result: %s', future.result())
             print(f"Processing result: {future.result()}")
 
+        log.set_log_level('stream_handler', LoggingLevel.ERROR)
+        log.logger.error('SECOND Start workers')
+        futures = [
+            executor.submit(work_function, log.log_name, worker_id, data)
+            for worker_id, data in enumerate(data_sets, 1)
+        ]
+        log.logger.info('[INVISIBLE] Workders started')
+        log.logger.error('[VISIBLE] Second Workders started')
+
+        for future in concurrent.futures.as_completed(futures):
+            log.logger.error('Processing result: %s', future.result())
+            print(f"Processing result: {future.result()}")
+
+    log.set_log_level('stream_handler', LoggingLevel.DEBUG)
     log.logger.info('[END] Queue logger test')
     log.stop_listener()
 
diff --git a/test-run/logging_handling/log_queue.py b/test-run/logging_handling/log_queue.py
index ab851a5..dfbe349 100644
--- a/test-run/logging_handling/log_queue.py
+++ b/test-run/logging_handling/log_queue.py
@@ -28,6 +28,9 @@ def main():
             # "console_color_output_enabled": False,
         }
     )
+    if log_q.logger is None:
+        print("failed to start logger")
+        return
 
     log_q.logger.debug('[QUEUE] Debug test: %s', log_q.logger.name)
     log_q.logger.info('[QUEUE] Info test: %s', log_q.logger.name)