How to return a game that for mistake was bought twice ?

I didn't even think you could buy the same game twice on the same account unless you were gifting one of them?

Hello Marco,

We understand that there is a double purchase for a game applied to the account and that you would like to return of these purchases.

It is our recommendation to confirm that there are two charges on your account through checking the
order history.

If there is a present extra charge, request a refund through our refund request webform.

Try these options and let us know the results.

Best wishes!

1. Sign in to the Xbox Refund Request Solution with your Microsoft account. Be sure to sign in from the account used to make the purchase. If you have multiple accounts, you can check the purchase history on each to find the charge and order number.
   
2. You will be prompted to verify that you are signed in to the correct account and have the order number(s) for this purchase.
3. Select the reason you are requesting the refund, then answer any additional questions that follow.
4. If your purchase is eligible for a refund, you will either be directed to the appropriate self-serve resource, or provided with a link to the correct version of the refund request form to fill out.

The link to the refund request could be open with this link: https://support.xbox.com/en-US/billing/payment-and-purchases/request-refund

i did the purchases within 2 minutes, it was misunderstanding. But now is every thing alright. They refunded me

Glad to hear and thanks for clarifying how you bought it twice.

https://support.xbox.com/en-US/billing/xbox-subscriptions/digital-goods-subscriptions-refund