I don't know why but every time I add an amenity to my town on here, it deletes it. Like I have the campsite and when I put the campsite as an amenity, it deletes it as if I never put it on there. Also it says my mart and garden shop is closed and it's not.

This might be a silly question, but are you making sure you hit the save button once you check your amenities?

As for the time of your shop opening/closing, do you have the correct "current time" set for your town? It could also be that you have an Early Bird/Night Owl ordinance that affects when your shops open or close. I don't think we have that accurately represented here.