I found a possible solution, but it is still not what i wanter as an answer so if anyone knows something better, please tell about it.
You can create a new animation and delete all the frames except one, so the animation will not has any moves. Then create a montage based on it and make sure it has the same slot as the animation montage you want to stop playing (if you have different montages with different slots, you will have to create a new montage for each). And after that when you walt to stop a montage, just call a montage you have created before. It does not have any moves, so it will be invisible. But still, it will override previous montage and then stop Instantly. So it will look as if you just called the “Stop anim montage” node, except you didnt.