The creditor can request fulfillment from the guarantor if the guarantor is obligated as the guarantor-payer because, in that case, he is responsible in the same way as the main debtor for the whole debt.
In any case, the creditor and the guarantor (as a third party) can come to an arrangement regarding a partial debt fulfillment. In that case, the debt of the main debtor is reduced for the amount the guarantor has paid and the creditor will, in exchange, return to the guarantor all collateral he has provided (debenture note; bill of exchange; statement for the confiscation of receivables…). In the event that the guarantor is also the pledgor and has paid the debt in full, the creditor will issue an erasure statement with which the guarantor will be able to erase the pledge on the pledged real estate.