freewares to adjust grey shades & brightness of an image

I used to use MS Photo Editor on my Win XP that could change the shades
& sharpness of an image.  There's also SnagIT on that Win XP.

But I left that laptop in my office & can't bring it back due to Covid.
I need to change the grey shades of a few images' background.

MSPaint & Snipping Tool can't seems to be able to do this or
can they?  Can advise how if they can do it.

Alternatively any freewares to do this?

Can we still obtain the MS Photo Editor to run on Win 10?
(as a portable rather than installer is good)