I moved your posts to the learning Japanese section.
1)
食べ物を食べる sounds awkward. I would say 食事をする instead.
It's OK just 買い物に行く for "to go shopping". If you want to use 店, 店 is the destination you go to, not the place you leave from, so から is wrong.
2)
You don't need to say あなた.
電車 is not the object of 遅れる (Hint: particle).
Use 帰ってください instead of just 帰って, since you are using the polite form in the second sentence.