anti virus

My android phone has been affected by a virus. I have tried some antivirus app on play store but could not solve the problem, am looking for a genuine way I can solve this problem. My phone is popping up some unwanted adds just like that. Your advice will be very helpful.

Guys, I have a Samsung A5 2017 and the problem is. Every time I try to download an application that's not from Google PlayStore the anti virus that came with the phone blocks it as a malicious file and can't be open. Do you know what's the solution to this?