2019 Imac keeps crashing with everything! Please help

I just purchased a new imac from Best Buy, It seems that the computer crashes on everything. It is the stock 2200.00 machine with a RAM upgrade i did myself.

I try to use Lightroom, crashes, Illustrator, crashes, Go Pro crashes, anything i plug into the rear, it crashes. I'm very frustrated. I did put in 128GB of RAM and i figured the computer would scream. Everything I try to do to be productive crashes the computer. I have taken one back to BB for a replacement but the new one is doing the same thing. Any help, tips, tricks, comments are appreciated.

Thanks!