Hi,
Can you try the following steps, please?
Step 1. Download and Save Avast Uninstall Utility onto your DESKTOP, from this link: http://files.avast.com/iavs9x/avastclear.exe
Step 2. Restart Microsoft Windows in Safe Mode: https://support.avast.com/en-ww/article/Restart-Windows-Safe-Mode
Step 3. (Only continue with this step if you are in safe mode ) Open/Run avastclear.exe and click on Uninstall
Once the uninstallation process is finished, please <Restart> your computer.