What's causing pop adds on my phone?

I deleted some apps that I recently installed but I'm still seeing adds on my phone. It's not just in browsers but in places like gallery when I'm viewing my photos. The weird thing is I started to notice this when I installed adaway. But I uninstalled this and other apps but it didn't help. It takes up the whole screen and i have to click no thanks to install whatever its saying to install. Any way to find out what's causing this?

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