Okiiee
I'm a newbie at them myself, and I'm also bad at explaining things but I'll try!
First and foremost, this applies to anything in art, wether backgrounds, perspective, animals or people.
-Reference
^This word right here is a euhhhh for a lot of people including me. But thing is this will help A TON because you are literally staring at something with the correct anatomy and shape! So if something looks wrong you check a real life reference to figure out what you did wrong it's painful I know.
Watch how things move, wether videos, real life you get. Study how other artists draw shade, and apply those concepts to what you already know. This is very important and every and any artist should try it if they want to learn how to improve.
Now sometimes when you see people sketch they use rough shapes to help guide them, I think that just everyone like to start off with circles for the head. I've learned this from watching videos and tutorials, but roughly starting with triangles and squares for hand seems to work.
Oh yeah for humans there's a physical difference between male and female. Females have a more hour glass shaped torso while males have broader chests and slimmer hips. (Idk how to explain)
I'd watch tutorials cause those things are probably much better at explains things like this than I am. XD

I sucks at it to but what i learned so far is sketch like crazy and at some point it fits ^^ not very helpfull is it??

Use anime as an anotomy example and use you for specific poses in the mirror. I suggest you start with a very simple one then move towards more of an slightly realistic style ^-^ I'm sure you can do it!

Im here to help anything you need me to do