Is it obligatory to make up two days of fasting: one due to the Maghrib Adhan that turned out to be incorrect, and another due to masturbating before Fajr and performing Ghusl after the Adhan?

Your fast is valid, and you are not required to make up for it. As long as you were certain that you broke your fast after sunset on the first day, your fast is valid, because what matters is the sunset, not the Adhan. On the second day, your fast is also valid as long as the intentional emission of semen did not occur during the fast but rather at night.