try to rig shoes correctly

hello i have successfully learned rigging through cg cookie turtorials. Now I started a more complex project. But I have troubles moving my shoes without distorting it. I don't know how to fix it. I couldn't join all shapes so I made an FBX of the model. but this also did not work in order not to distort it. What is the correct way to do it? thank you so much!


i didn't find a solution here in the courses or not even on YouTube.