Исправьте ошибки.

 You don't can go to the party.

Where do you must be?

You can't use a computer?

He can play chess when he was Five.

Can I come in?

You can't go to the party.Where you should be?You can't use a computer?He could play chess when he was five years old.Can I come in?

вроде бы всё правильно, но 2 предложение с конца мне кажется не совсем правильное)