Animated model keeps sinking when I get near it, also my animations have no colliders

To start, I made a low poly zombie in blender then uploaded it to mixamo to get some animations, everything I imported to unity came from mixamo. I then made a script so the zombie follows the player, and the animations work great but the issue is every time I walk near my zombie, it starts to rotate on its y axis and sink to the ground. Thats one issue, the other is I dont know how colliders work for imported blender files, I tried adding a mesh to my zombie but its mesh came in really tiny between its legs. When I went over to the inspector for the zombie model, I tried the generate colliders option but it did nothing. Im mostly concerned with the sinking issue. The mesh and colliders seems to be that I dont know a better way of going about it.

ground sink issue


mesh collider is tiny issue(it also comes in facing the ground)


The insides of my zombie poly, its mesh is still facing the ground


my zombie inspector