Student visa

My son has recently received the one-year student visa category D on the basis of conditional university offer/language school and traveling to Berlin end of January 2025. Now he has also received the confirmed admission letter for another university HAW Hamburg university for the same subject (BSc. Mechanical engineering) starting April 2025. Kindly advise if he can travel to Germany on the earlier issued visa and can complete all visa formalities for new university admission in Germany?