Answer 1

No, I don't think you're in danger of getting pop-up ads. I recommend that you uninstall your virus scanner which is the more serious danger. Just don't click on the ads, then everything should be ok.

Sololearn won't be that stupid.
Most or even all ads are placed by Google.

Of course, it can always happen that a virus gets through. Especially when Google is too lazy to check the advertising sources.

Don't forget to install software updates regularly and don't forget to back up your data regularly.