"my school in big hall" is not a sentence. It needs a verb. It also needs a capital letter at the beginning and a period at the end. (Did you read Clive's post?)
Do you mean to say "My school is in a big hall"? That is a sentence, but it does not have the same meaning as "My school has a big hall."
Please make your questions more clear. When you simply post a phrase it is difficult to guess what kind of help you are looking for.