Change UE4 Mannequin to a Mixamo Character

Hey Unreal Community,

I have a big issue with Third Person Character. I want to change the ue4 Character to a Mixamo Character but to keep the standard animation blueprint, because I worked with this blueprints. Now, when I change the Character Mesh, my Character has no animations anymore. My second problem is, that I cant import Mixamo animations. Not even, when I upload the Ue4 Character and then download it with new animations. Everytime there comes this message:

PS: Sorry for this english