Andriod users seem to be inflicted ” sometimes ” with pop ups and ads from strange websites on their smartphones , so what can you do about this ?
First go to your internet browser on your smartphone and clear your browser history and everything it stores , also clear any saved websites you have.
Here is a link from Samsung to assist:How do I clear the cache, history, or cookies on the internet browser on Galaxy device?
Next look for rubbishy apps such as cleaning apps and delete them as they are not needed and really if it didn’t come with your Android phone you probably don’t need it.
This should get your phone back to normal
If not make sure you have backed your phone up to Google then wipe and reinstall on your phone