Invisible device administrator virus keeps opening a web app every time I unlock phone

[Android Central Question]

Well, I can't believe I fell for it but I downloaded an apk file from an unknown source (apkmb.com). I downloaded the apk file and enbaled the app request to be a device administrator. I tried to delete it but it still shows on the list of device administrators although unticked. But every time I unlock the phone, a web ad shows in chrome.
Can anyone please help me?

 

[B. Diddy]

Welcome to Android Central! Which phone? What happens when you try to uninstall the app in Settings>Apps?

Ultimately, you may have to do a factory reset.