Assets Black And White & Preview Fix Needed

I bought a lowpoly asset pack to use for my game, but whenever I drag the assets into my game, they turn black and white with no textures applied on the ride side. Ill post some screenshots that show whats going on

once i drag it the image at the bottom also goes black and white and it has no colour, please help me thanks.

Also when I use an asset, when shadow goes over it sometimes it says Preview in certain spots, how do I also fix this?