Проверьте орфографию: when on the beach piease you mustn't throw litter into the river. you mustn't disturb others. you must follow the rules. you mustn't lead to the beach for their pets. you mustn't make a lot of noise. это мое "написать несколько правил поведения на пляже" правильно ли? если нет,то укажите на ошибки,.
Mustn't в данном случае лучше заменить на shouldn't.
When on the beach, please remember that you have to follow the rules. You shouldn't throw litter into the river. You shouldn't disturb other people. You shouldn't make (a lot of) noise. And you shouldn't bring pets with you.
Я б так сделал.