I know how to Rigging a Blender 3D, but after testing it, it worked well, but the right arm doesn't look like a problem in the armature, but it gets crumpled in a strange direction. And I thought it was the mirror, but it wasn't. I kept looking for a solution, but I couldn't find it. Please help me as soon as possible. Thank you very much. I'll leave a screenshot. And Please Give .blend file
First, select the arms and Clear the Parent.
Now select the arm again and Set Parent To Bone.
I think the vertex groups are not painted well.
I repainted the meshes but the result was not so good.
The best thing I could do is to reparent the objects.
See the image below:
It's a good practice, as soon as you unparented the objects, to delete all the vertex groups of that object.