@jiis the patrol behaviour doesn't play well with physics. I'd suggest maybe using the set velocity behaviour on a timer instead, something like this:
Basically, it multiplies horizontal velocity by -1 every second (or however long you want the patrol duration), but also switches when it collides with something on the left or right.
Colliding also runs the behaviour on for the Wait2, which has the effect of resetting the wait so you don't run into the issue where it bounces and then changes direction again right after.
You might want to use a tag in the collided behaviour so you can tag whatever objects should cause the enemy to bounce, or just get rid of it altogether.
The reason I put set velocity on a timer like this is so you don't have to worry about friction and air resistance slowing the enemy down.
I'm not great at explaining things so let me know if you need me to explain further. Here's a link to that project, behaviours are inside the red square object. http://bit.ly/2HLIM5e