Hi Katja,
I just replayed the levels. Here's what I came up with:
W10L2:
Begin by pushing the boulder marked in purple counter-clockwise. Follow it around and push the other boulders counter-clockwise as well. This results in a boulder placed at the blue X. Once in the center. Use the metal boxes to guide the boulder to where you want it.
W10L3:
Place the reflectors as shown. Place Stinky on the purple X and make the UFO fire two shots. That leaves you with plenty of boxes to put one at the yellow X and collect the bonus coins.
Let me know if you need further help, I'll be happy to give it to you.
Mette

You do not have the required permissions to view the files attached to this post.