What is the ruling on the songs that he downloaded and saved on his device, after deleting the program that was given to him, knowing that the one who gave him the program advised him that songs are forbidden?

You must repent, seek forgiveness, and strive to retrieve the program you gave him. You should also retrieve everything that person might use to commit haraam acts, including the songs that were downloaded via the program. If you can convince him to delete them, that is your duty. Otherwise, we hope Allah accepts your sincere repentance.