What is going on with my phone?

[AC Question]

So randomly one day i was trying to get onto YouTube but the thing would not load. I had full WiFi bars and everything. I tried to find out what was going on on the internet but that took ages to work also. but when i tried to send a text, the screen had a lag spike for maybe 15 seconds on a white screen until it eventually popped up but it wouldn't let me type. when it did finally get through it took like 10 minutes for my text to get through on full bars. All the while in about this 15-20 minute time span, my battery lost 25 percent. No joke. I would really appreciate some help because this is very frustrating