How to import into blender with texture .obj .Mtl

If you want to use Cycles, you have to reassign the textures.
There is no other way. Obj or fbx cant store the node system that cycles use.

Maybe the old render from blender could handle it.
But this is not cycles.

Ok so how do I figuer out what textures goes to what ? element ?

Hard to say whithout knowing what textures your modell uses.
You could try the new principled shader and put your textures in the correct slots.
Or you creare your own Node system in Cycles.

Did you try to contact the seller and ask for support?