ارجوكم ساعدوني
 

need to : expresses necessity in the present or the future.
I need to know how many people will be at the party.
محتاج ..

have to : expresses external obligation in the present or the future.
You have to drive on the left when you`re in England. (It`s the law).
إلزام من طرف خارجى (الدكتور / القانون / قواعد المرور)

must : expresses personal obligation in the present or the future.
I must finish this by tonight. (I say so).
إلزام أو أهمية نابعة منّى / أنا اللى حددت ذلك

ميرسى بجد والله ماكنتش اعرفها ميرسى لحضرتك