Update on my Laggy Phone!

Hey! As you may have read here, my phone's become laggy recently. I thought it was Instagram but don't think it is anymore. Anyway, it freezes for up to two minutes at a time every so often. Anyway, I found out that if I leave it, it eventually restarts the launcher or something. The screen goes black, all buttons disappear and then the lock screen appears. After that, it's back to normal until next time. Any ideas? I desperately need you help, thanks!

Edit: It just froze for a good five minutes and then this appeared https://m.imgur.com/gallery/Tpd74 I checked the RAM Usage using CleanMaster and that's the other photo. Is this normal and does it change anything?