Hi Maciej,
I'm Adie, and I'm happy to help you today.
Sorry to hear you're experiencing this issue. You may open Word in Safe Mode to determine if the add-ins are causing the problem. Press and hold the Ctrl key and double-click the Word shortcut. To ensure Word is in Safe Mode, you should see something like Microsoft Word (Safe Mode) in the title bar.
Check if the issue persists while in Safe Mode. If not, add-ins may be causing the issue. In Word, go to File > Options > Add-Ins > Manage: Com Add-ins > click Go. Uncheck all the add-ins. Close Word and restart it in Normal Mode.
If the issue persists, perform an Online repair of your Office. Kindly refer to this link.
https://support.microsoft.com/en-us/office/repa...
I hope this helps. Please let me know if you need further assistance.
Best regards,
Adie