O+ USA Android 8.96 Has A Virus

Years ago, I connected to an internet at my aunt’s house. And then after I connected my phone, many pop ups came, unwanted apps installed, and can’t get rid of them even though I remove them they still keep coming. Soon I rebooted my phone and some of the phone’s main apps such as browser, google play store, calculator and calender is gone! And some strange apps are there that looks like android. My phone has a virus named google provision which is hard to remove. Now when I download apps or games it always said : Unfortunately, app has stopped or goes back at my home screen and stops working!! Pls help me how to fix this. Thank you!!