Humanoid Army and Police Robot Free 3D model

this model has been an absolute waste of time for me, no matter what i do, after i export it to fbx from blender, it loses 25+ bones and is absolutely useless in unreal engine. I'd be really grateful if someone knows how to fix this god forsaken problem of mine. I might be new to blender and unreal but after spending 2-3 days trying to figure this out watching countless tutorials and reading up on reddit and nothing I've found has fixed the problem, its easy to come to the conclusion this is useless. I was really excited for these models though

great!

They look fantastic!

can I use this for my FPS game Metal Madness? (its a shooter game that takes place in the future with robots)

Mind blowing !