You're not doing that much wrong, don't worry! You're doing quite well for a beginner, you're just getting ahead of yourself, which can lead to bad habits and slower growth later on.

Thank you for your feedback (really I'm glad you take the time to give me feedback). I didn't know there's so much I can do wrong xD silly me xD
So, simple, with clusters of pixel and no dithering before it looks good without :) alright, I'll give my best :)

I think you overdid the dithering on/near the hair a bit. For the hairline, you might not need any shading at all. For the hair part in the middle, I suggest using a solid shadow with irregular edges (to suggest some texture to the hair) instead of the dithering. Try making the hair shinies solid too. With highlights, the shape is often more important than the intensity, a well-placed too-bright highlight can look better than something of the "correct" value that has a poorly defined shape (and with dithering, defining small shapes is very difficult).

I think you should focus on working without dithering for now. Think of dithering as an advanced polishing technique rather than a basic one. A pixel art piece that looks good without dithering can transcend to the next level with judicious dithering, but dithering can't save something that doesn't already look good without it. So for now, focus on making the most of the fundamental building blocks of pixel art - solid clusters of pixels.