I don't know much about computers, maybe I did something wrong?

I have an iMac Mid 2011 and I installed macOS Sonoma 14.7.5, now I'm trying to open some apps I had before installing the new system and I can't open them anymore. Also I downloaded (app for DJs) tried to open it but it gives me an error while opening and gives the option to reboot it. I don't have much experience with computers so be patient please and help me.

3,4 GHz Intel Core i7 quad-core

AMD Radeon HD 6970M 2 GB

16 GB 1333 MHz DDR3