Can someone check these sentences for grammar and context?
1. Tu n'as rien (as in you don't have anything).
2. Nous ne voulons acheter rien dans ton magasin (as in we don't want to buy anything in your store).
3. Tu ne peux pas aider moi (as in you can't help me).
4. How can I say I don't have clothes in a certain size in French?