Photoshop quality loss???? At my wit's end!!!

[kennyren]

Hey guys. I've been having an issue with photoshop where painting dark parts of a drawing makes the darkness level too high. Here is an example:

As you can see, the white is fine however when I use the black brush the inside's quality gets very dense and contrasting (I don't know the word for it )

Which makes my drawings look very bad when I try to add darker gradients:

And in darker backgrounds I can't even do a proper gradient without it looking odd:

Please help, guys. I'm at my wit's end

[c.pfaffenbichler]

What are the file’s Color Space and Bit Depth?

What are the Brush settings (Blend Mode etc.)?

Manual strokes are not completely reliable, could you create a Path, »Stroke path with brush« on a 50% grey background with white and black and post the result, not a screenshot, but the actual image?