I found an awseome drawing online and I wanted to recreate it in inkscape.
But I don't know how to draw the detail so well. I'm talking about shadow of the cloak, lines in the cloak etc.

Check out Jason Secrest's youtubechannel for inking and colouring cartoons. His tutorials are awesome !

https://www.youtube.com/user/jasonsecrest/videos

Its for Illustrator but the principles are the same. Instead of Brushes you use Pattern Along Path. Instead of the Knife Tool you use Boolean Operations. Etc.

Thx, I will watch it.

my progress:

It looks like you've made a good start. I don't understand what you don't understand. It looks like you already have the skills that would be needed. For the shadow, you just draw another object on top of the cloak....well, if the shadow is on the cloak. If you mean a cast shadow, like the shadow of the cloak on the leg, then you draw it on top of the leg (for example).

For the shadow and the lines on the cloak, the cloak should probably be a lighter color, unless you have sort of a negative effect in mind.

On this page: https://forum.inkscapecommunity.com/index.php, in the Cartoons - Comics - Game Art section, there are loads of tutorials. Well, there are loads of tutorials on that page in general. But in that section is likely where you'll find similar types of drawing styles.

It's probably a good idea to ask the artist if you can use his/her image. Otherwise, you can only legally use it privately. (Technically, shouldn't even be posted here without permission.)

Edit
You posted just before me.

I'm kinda new to inkscape and also drawing that's why I asked here for some tips.
When I started I had no idea how to do it, but I just experimented it worked.
Thank you for the link, it will be a great help.
(I will also ask permission of the artist)

I worked a bit further on it. I'm not so sure with the "holes" in the armor. Do you guys know a way to make them better?
Also the eye is bothering me a bit, should I add an outline or start in a different style?
(sorry for all these questions, if this bothers someone, I will stop asking.)

In my opinion you are getting lost in detail.
If you look at the overall image, its cool because its this depiction of a larger than life manga hero, standing on a cloud and wielding a huge sword.

Thats why i would start inking the whole image first, because the lineart is really the key ingredient of the artwork and make it as cool as possible.
Right now your inking is inconsistent. Theres no outline on the eye for example.
Also using different shapes and width for the lines can make a nice effect (an ellipse or half an ellipse for the Pattern along path).

The colouring is the next step and perhaps it would be good to think about a restricted colourscheme first.
There are sites dedicated to colourschemes/palettes or use something like this:
http://paletton.com

Remember, your traditional marvel comics where limited to four colours, for example.
It can make things easier.

I would also stay away from gradients in this example.

Instead of tones for the shading, you can also work with textures (like a micro checkerboardpattern for example).
You can see that a lot in black and white manga.