Fps tanked after windows reinstalled

I had to reinstall windows on my nieces laptop because it had some problems to say the least. I downloaded everything back and now her fps on roblox is laggy/choppy. I even turn down the graphics slider all the way down to one and it was just as choppy as it was in the middle of graphics slider. Please help I have no idea what to do considering it ran just fine before the reinstall. (It’s a dell latitude 5420 i7-1185G7 16gb ran 256gb storage)