For starters, I would recommend installing Darktable or RawTherapee (both are free). If you want more power over individual pixels and want layers (very useful for major cloning work), Affinity Photo would be a good one to try out. (for about 50$ USD). It takes a while to learn how to use them, but once you have learned these programmes they offer a plethora of tools and you will wonder how you ever did without!
For a run-down of a few programmes and what they do, take a look at this post:
https://www.lenspiration.com/forums/topic/photo-editing-2/#post-30264