Answer:
A useful formula is in english write 'que than' because que sounds sort of like "'curd" in english, and for qui, it sounds like key. So, remember 'Key and curd'
Ok so the first sentence is "I have a girlfriend who is French", and the second one is "This is the book he’s going to buy"
Qui means who, and que means than, but I don't see que in either sentence.