In the Task Manager, behind the Applications tab, there is a Processes tab. On that one, look for firefox.exe and plugin-container.exe. Any luck?

After that, you should be able to start Firefox normally without having to uninstall/reinstall. If you encounter similar hangs in the future, you could try using Firefox's Safe Mode to see whether Firefox works normally without add-ons.

You also can terminate any running instance of Firefox by restarting Windows. Afterwards, if Firefox starts running silently without you starting it, that could indicate a malware infection.

That ws graet and solved my problem. Thanks. How do I mark this solved?

Looks like you found it, thanks.