You have signs of infection on your machine, and this will take a while to clear fully, but stick with it, and we should be able to remove it.
Avast is not a particularly good AV product, and sells on its User's data ...
.... I believe you would be protected better using Microsoft Defender, which comes with Windows 10. It is of course your choice as to whether you wish to keep it, but if you do choose to remove it, then please use the Avast Uninstall Utility .... instructions for which can be found .... HERE
Once it is uninstalled, Microsoft Defender will automatically switch on to protect your machine.
If you choose not to uninstall Avast, then just follow the instructions below ...
Please run a scan with ADWCleaner
Download AdwCleaner and save it to your desktop.
- Double click AdwCleaner.exe to run it.
- Click Scan Now ...
- When the scan has finished a Scan Results window will open.
- Click Cancel (at this point do not attempt to Quarantine anything that is found)
- Now click the Log Files tab ...
- Double click on the latest scan log (Scan logs have a [S0*] suffix, where * is replaced by a number, the latest scan will have the largest number)
- A Notepad file will open containing the results of the scan.
- Please post the contents of the file in your next reply.