How to link a segment to a bone to get a better result? I'm making a rig in blender, pretty simple one, the only problem right now is this:

You can see it's pretty messed up.
I want to get to this result:

So I think I need to rotate the loop cut in the middle of the arm, or something like that, but I want it to be automatic when I rotate the bone. Could anyone help me please? I've been stuck on this for 5 days. (No joke, I'm still a begginer, and everywhere I look, it's either for v2.7 and below, or they use a more complex rig and thus blender works fine.)
Maybe simply shearing the edge loop at the elbow?