You can goto the URL opera://about, take note of the "install" path and close Opera.

Then, you can uninstall Opera (but don't choose to delete your data when asked). Then, delete the install folder.

Then, delete everything in "C:\Windows\temp" and "C:\Users\yourusername\AppData\Local\temp".

Then, download Opera GX in whatever browser you want, launch it, click "options", review and adjust things how you like and reinstall.

Doing that might fix things.