Can someone please explain why this is happening? And a Solution?

I have downloaded a model off of renderhub (3d model website), i put it into blender, then to mixamo, then to ue4. I downloaded an animation off of mixamo and imported it to ue4. And this happened. Can someone please explain? And what can I do to fix this?

P.S. I don’t want to use the characters off of mixamo

If the model is hust a mesh and didn’t come with a skeleton you have to rig it yourself.
If it has a skeleton you have to retarget the animation to the skeleton you are using, as Mixamo animations use Mixamo skeleton by default.

Did you download it with “With Skin” checked? I recently brought many models from MakeHuman to Mixamo to Blender to UE and had no problems with the skeleton.

I think the skeleton of the mesh and the skeleton of the animations are different. My guess is that you have an additional group in either one.