Is it permissible to combine the Dhuhr and Asr prayers, and the Maghrib and Isha prayers, due to the necessity of attending educational courses that last from three o'clock until seven or eight, which conflicts with the times of the Asr and Maghrib prayers?

If you fear that your abandonment of Shi'ism will become known, and you cannot find a safe way to perform prayers on time without harm, then there is no blame upon you for combining the Dhuhr and Asr prayers, and the Maghrib and Isha prayers. Fear for oneself is considered among the excuses that permit combining prayers, as mentioned by jurists. Al-Bahuti stated that combining two prayers is permissible for someone who has an occupation or an excuse that permits abstaining from Friday prayer and congregational prayer, such as fear for oneself or one's property, or suffering harm in one's livelihood.