Hi @lunahak ,
These models are made for Blender, using a lot of Blender-specific ‘tricks’ (most notably Geometry Nodes). They cannot directly be Exported, they will have to be heavily ‘adapted’, aside from the Unwrapping and Baking the Materials and this is not something that I can explain in a thread like this.
It’s probably better to find assets elsewhere, or (and this is really fun!) learn how to make your own (Export-friendly) models.