I need toget some sleep.

He needs to get some sleep. 

He said he needed to get some sleep.

If you have questions, you need ask.

Youneedn't pay for that phone call.

You don’t need to for emergencycalls 

I reallymust stop smoking

I reallyhave to stop smoking.

I had towalk in the rain.

Do I have to go to school this Saturday?

Must I go to Schoolthis Saturday?

Yes ,you must. \Yes, you have to.

 No, you don't have to. \No, you needn't

Youmustn't / can't take photos in the museum.