Must I repeat prayers that I erroneously prayed facing the wrong Qibla for more than a week, and are prayers whose validity is doubted to be made up for, or are supererogatory prayers sufficient?

If the error in the Qibla arose from following a trustworthy friend, then according to the majority of jurists, there is no need to repeat the prayers. This is because for someone who is not proficient in independent juristic reasoning (ijtihad), their duty is to follow (taqlid), and it is a condition that the person being followed is trustworthy. As for doubting the validity of past prayers, it holds no weight; it is a whisper from Satan. It is recommended to perform many supererogatory (nafl) prayers.