These days almost every time I go to download or even watch an online movie Avast stops me, saying it is blacklisted. How to proceed?

YOU learn how to use Avast!

If you look in your Taskbar Notification area (normally at the bottom right of your screen) for your Avast icon, you can right-click on it and select disable Avast shields control for 10 minutes, 1 hour, until your computer is restarted, or permanently.  Do be aware, however, that this WILL put your computer at risk of viruses being downloaded onto it.