The mesh isn't moving together/ as fast as the bone so I'm trying 2d animation and Iam facing a problem now. Which is that when I'm in pose mode and I move the bones of the hand, the mesh of the hand moves, but when I move the bones to high, the mesh doesn't follow up and has like a gap.
If you use Vertex Group in Armature Modifier, be sure Weight Paint of the object is absolutely red.

Or leave Vertex Group field empty.

Be sure other bones (small one) doesn't have influence to the object. Select Armature + Object, switch to Weight Paint mode and click on other bones to see if object is completely blue.
In your case Delete Armature Modifier called &quot;Armature&quot;.