Avast blocking my computer

Some times ago I was taking Avast for Free to protect my computer.
In the beginning it was going well but after a time I was forced to take an abonnement on Avast (19,90 euro) because my computer was very slow and was continiously blocked.
After I paid, the problems became worser and Avast asked me to buy other security-services, what I refused.
I can no longer work on my computer on this moment. He is continiously blocked by the Avast control system.
I wrote already to the board of direction of Avast because the desinstallation of Avast is also impossible. Avast refuses my password.
If everything woudl work corerectly, I can keep my Avast but NOT in these conditions !

This is probably the wrong forum for you. Endpoint Protection is a business product. Avast free/pro/premiere is likely the correct forum.

That said, have you tried the uninstall utility?
https://www.avast.com/en-us/uninstall-utility