Do you want to extend your stay? How to translate it properly?

1 Are you going to stay? How many days will you stay if necessary?

Will you stay with us a little longer (sir/madam)?

or

Are you going to stay with us longer, sir/madam?

If so, how many more days?

I want to extend my stay for two days. How much do I have to pay?

I want to stay for two more days. How much will that cost?

or

I want to stay for two more days. How much will it cost?

In addition, several related sentences are provided:

Is there a discount on this?

Do you have a special price?