How to stop pop up ads

Hello,

I don't know if i am on the right place here but it's worth a shot.
Since a few weeks i get full screen pop up ads that say that my phone is infected and that i have to instal anti virus apps.
I hope that someone can help me and get rid of the pop ups. I have already uninstald every app that probaly could cause it but the pop ups keep coming up.

With kind regards,