I found the answer by myself. I didn't use move_and_slide also I didn't know the basic use of it:
the first parameter is a Vector2 and it define , if I'm not mistaken, the speed direction of speed of which the object will move/slide.
Now someone can tell me how I can increase the default space between each moob?
edit: found the answer by myself again :) But I'm not sure is its the correct method:
Increase the collision shape size. It is the correct method?
Thanks