what is a good photo editing software to buy ?

Affinity Photo by Serif. You pay for it ONCE.

Corel?

Want free? Gimp.

There really is only one, Adobe Photoshop. I understand they don't sell it anymore, you only rent it month by month for something like $20/month (which is cheap enough if you use it).

I used Adobe Photoshop 15 years ago on my job--just for simple things like adjusting contrast and brightness and 'levels', cropping, etc. But I went through one of those 1000 page manuals and learned to do all kinds of things. It became recreation as well as work.

Just recently I got back into Photoshop, and there are so many new features! They've been working on it continuously. Meaning nobody will catch up with them. Photoshop has every bell and whistle you can imagine, and quite a few you'd never imagine.