Why is my phone downloads apps on its own?

I was about to download a game called pokemon black on my my phone but my hand slipped and accidentally downloaded something called android.com/apk, then everytime i open my phone's wifi that thing always pop up ads, download useless apps, it also downloads an unnamed app with android logo in it and when you didn't close it or uninstall it you have to turn your phone off again, if you unintall that android logo your phone will become worse it will hang and the install again without my permission