1. eat/ enjoy/ you shouldn't / you / much/ can/ you/ the food/ but/ too/ have.

You can enjoy the food you have but you shouldn't eat too much.

2. can't/ the piano/ Nhung. sister/ play/ and/ her/ either/ can't

 Nhung can't play the piano and her sister can't, either.

3. went/ she/ stomachache/ the doctor's / an/ Lan / because/ awful/ to had

Lan went to the doctor's because she to had an awful stomachache.

4. have/ the farm/ often/ them. vegetables/ from/ dirt. on.

Vegetables from the farm often have dirt on them.