Not steady aim, grip is good but arms are not stable enough

[Saur]

I sometimes have a not steady aim and have the feeling that my arms are the problem for the movement and not the grip. What can I do about that?

Try some of Keith Sanderson's holding drills.
https://www.youtube.com/watch?t=105&v=620LlSK3Oyo
https://www.usashooting.org/library/...t_oct_2009.pdf

[Gio]

Unless you're shooting competitive bullseye, you're probably steady enough. Your real problem is likely not being able to press smoothly through the trigger while accepting that sight movement.

One thing you can do to visualize your actual wobble is to put a laser on the gun and hold a sight picture on target at the distance you're shooting. The laser will tell you just how much movement you have.