An app always pop up everytime I unlock the screen. How can I fix this? (Galaxy S7)

[AC Question]

I downloaded an apk file and it downloaded another app which I deleted already. Afterwards, an app (Some kind of a browser showing different ads) always pop up right after I unlock my screen. It can be easily closed but it's really annoying to see it everytime I want to use the phone. Thanks

 

[dexterouz]

I have encountered this kind of thing with some cleaner app. I uninstalled it and looked for the alternative.
Some apps by default enable those option, check the app settings if you could disable something related to it.
If there is any app then you can go to phone settings > installed apps and look for a suspicious app that you haven't installed by yourself and uninstall it.

OR else, if the app is some kind of 3rd party lock screen or lock screen notification related then they might be showing you the ads, which can't be disbaled unless they have a donated version of it.