can you explaind for me, when i should use MUST OR HAVE TO?

What's the difference between when we use "must and have to"?

Can you explain? when should I use Must and when should I use Have to? (to me your question sounds better in this way)

What's the difference between Must and have to?

Use 'have to' in the past, present and future to express responsibility or necessity. NOTE: 'have to' is conjugated as a regular verb and therefore requires an auxillary verb in the question form or negative.

We have to get up early.

She had to work hard yesterday.

They will have to arrive early. Does he have to go?

arrive before 8. They didn't have to work so hard.

The negative form of 'have to' expresses the idea that something is not required. It is however, possible if so desired.

You don't have to arrive before 8.

They didn't have to work so hard.

Use 'must' to express something that you or a person feels is necessary. This form is used only in the present and future.

I must finish this work before I leave.

Must you work so hard?

The negative form of 'must' expresses the idea that something is prohibitied - this form is very different in meaning than the negative of 'have to'!

She mustn't use such horrible language.

 Tom. You mustn't play with fire.

Hope this helps! Best Wishes!