(The problem has been solved) I had set a password to access the Avast application settings on my computer, but I forgot the password and now I can't access the application settings in any way!

To access the settings of the Avast application installed on the computer, we can add an extra security password. I had added such a password because I didn’t want anyone else to change the settings (note: this is not the Avast online password, it’s another security password for the application). I forgot this password and couldn’t access the settings or uninstall the application, but the solution was quite simple:

1- Download the Avast application uninstall tool.
2- Run the application and select “Start in Safe Mode” from the three options.
3- Your computer will restart, and the Avast application can now be uninstalled.
4- You can reinstall the application in normal mode and use it as before.

Create a new password. How to reset or change your Avast Account password | Avast

No, that’s not what I’m talking about. This is resetting the Avast Online (Web) account password. What I’m referring to is the password for the application settings themselves. The Avast application, under Windows, allows you to create an additional password to restrict unauthorized access to settings as an extra layer of protection. That’s the password I’m talking about.

This is not an easy process.
Regaining access to the Avast program UI without a password - https://support.avast.com/article/password-protect-antivirus/#pc

Having set a password to prevent access to your User Interface settings. there is no easy way to recover from that other than a Clean Reinstall