I am sorry. My corrections are in red. I didn't delete them as sometimes I have to ask whether either can be used. I will delete them if they are confusing. Should I?
OK, then if the red is your choice(s), then these have wrong components:
2.There was a/the discotheque at a/the club last Saturday but he didn't go. (Actually, I think discotheque = club, so I don't understand the sentence.)
5.There is a jar of the/a /- orange marmelade in the middle of a/the shelf.