dell inspiron 15 7000 wont work

I bought this laptop about 3 years ago, just a little under that. It worked great when I first got it. I use it for homework and games. Now though, it is very difficult to run anything. I used to play skyrim on here no problems and now it wont even start, it takes forever to load anything, and it is painfully slow to start. I have tried everything I can think of: checking for virus and malware, making sure everything is updated, going through support assist to check for issues, f12 at startup, i havent used even half the amount of storage, i even tried resetting. nothing has worked. Any suggestions?