Avast is driving me crazy

I just purchased the professional Edition of Avast and now I am completely frustrated!!! The websites I frequent no longer work correctly, I cannot click on buttons, the site won’t download all the way, and no scrolling pictures or video work. I have tried to turn off Avast but it still does not work. Some websites are just a blank page. I need help!

Did you have another antivirus software before? If yes, how was it uninstalled?

Do you have a firewall?