Car Seat for Dogs up to 19kg

My dog is a corgi, 13kg and can’t fit on the bed.

The dog was on the back seat with these seat belts and managed to get so tangled up that its leg almost got dislocated. So you really need a separate safety belt to secure the dog, because the straps on this seat don’t work and can even be dangerous. I also don’t really understand the attachment system—how are you supposed to fix this to the seat?