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Thank you. I've been able to fix a few things, but none of them completely. I can't or, more likely, I don't know how to use the editing program.

Actually it can't be solved at all, but with photoshop there is something that helps, menu image - adjustments - curves- This measures the shadow and light curves, you can try with that.

I use Lightroom but haven't tried to learn too much, I usually do simple retouching.

I don't retouch simply if it comes out too dark I fix it by giving it some highlights or contrast but nothing else, although I try not to do it.