I think you are looking for an auto-clicking program like GS Autoclicker but I am not sure if they are compatible with opera? It works fine in games for sure.

Sometimes I face that issue too. But I simply close the browser and restart it and everything is fine. I think it is more of a device issue because on my other mobile it never happened. Or it could be the website from where you are downloading it( Could be malicious).

You can try to clear your bookmarks, History. This might help. That's the only logical thing I can think of.