Reformating and reinstalling is what you do with Windows. Something I can spot instantly is 2GB RAM is far too little to do anything with even Sierra OS. Yes, yes, it meets Apple's "minimum" but realistically that gets the computer to boot and to run Text Edit. I'd say with Sierra you need at least 4 GB for any kind of reasonably minimal performance (run one application at a time) and 6-8 GB for any serious work. With too little RAM your computer resorts to using the hard drive which is likely an older 5400rpm mechanical drive which will be very slow as well as hard on the drive.
You can also run this tool to do a system check to see if there's something else but I think you really need a RAM upgrade. You could also consider swapping your drive for a SSD. I'm guessing you could maybe do both for just over $100 as long as you weren't going for a ton of RAM or a huge drive, and DIY.
Run this analyzer and post the results here.
http://www.etresoft.com/etrecheck
EtreCheck on the Mac App Store - https://itunes.apple.com/app/etrecheck/id1423715984?mt=12
Using EtreCheck - Apple Community
To save posting really long reports to the regular window, use the "paper" icon in the editor bar. See: https://discussions.apple.com/thread/250225837?answerId=250419632022#250419632022