The value of the loans stay the same. Deutsche Bank takes a loss to get rid of the loans for cheaper.Can someone better at finance/banking than me point out if this is a credible interpretation of this? It would seem that he'd still owe the debt in question, just to other entities than Deutsche Bank instead...but probably I'm wrong.
As the buyer would pay less for the loan they might be up for a cheaper repayment to avoid not getting anything at all but that is speculation. Legally the loan keeps its it value. There is no reduction in debt unless the buyer somehow gives Trump a easy way out.