Q: why my payment method its decline

I suspect you are trying to use a DEBIT card and not a Credit card.   Many debit cards are no longer acceptable.  Have you checked your billing details to see if your card is in the list of acceptable ones.   Go to App store > store > view my account > sign in > edit payment info.   There you will see the currently acceptable cards for your country.

Try updating your billing information:

Change or remove your Apple ID payment information - Apple Support

If you are using a card that is listed as acceptable and it still does not work, your first check is with the card issuer.