My android phone suddenly began to display some pop up ads on the screen, when ever i enable data connection on my phone, the ads never stops coming, instead it kept on interrupting me when ever i am surfing the net, chatting on various Social Media sites, typing and so on, it never stops coming except data network is disabled, the most annoying thing about these attack is that it automatically begins to download and install applications at random to the extent that it consumes a whole lot of data in few minutes, sometimes it does install malicious applicaton to my phone.

which would be an access for hackers to monitor my device usage, which includes the Email i receive, passwords.
But the following post expains the best way to stop this
https://www.mariotek.com/2019/02/android-phone-automatically-downloads-application-and-pop-out-ads-problem-plus-solution.html?m=1