Is it obligatory to say "So-and-so taught me" or "Allah taught me" when receiving knowledge from a teacher, and which of the two is more correct?

There is no harm in using the phrase "So-and-so Sheikh taught me," for the Sheikh's teaching is from the grace of Allah, as He—the Almighty—said: "And Allah created you and that which you do." The attribution of teaching to the teacher has been established in the Sunnah and the words of the Salaf, as in the hadith: "The best among you is he who learns the Qur'an and teaches it," and the saying of Ali, may Allah be pleased with him: "Shall I not teach you words that the Messenger of Allah, may Allah's prayers and peace be upon him, taught me?"