Help with FPS Controller with Full Body

So I tried changing the assets from the standard assets from the unity, the third person one, but I am facing issues. I want to make a fps with full body with a body I have from fuse cc, but when I change the models it stays on idle animation and if I try to move backward it bugs very hard.

I am posting a video down below:

Please, someone help me.

I tried to do the full body like you before as well ,but as me and i guess everyone else you will find out there are too many issues. Check out this video Unity3D - How to add legs to a first person view in FPS kits (MMMFPSK) - YouTube
the point is to use the character body twice with two animators one for hands one for legs /rest of the body which will show the shadows. After checking several GDC talks i recognized that is how AAA studios do it as well