السلام عليكم ورحمة الله وبركاته ‎ أحسنَ اللهُ إليكم In the summer, they combine Maghrib and Isha for three months. Two years ago, I prayed a lot with them because people convinced me that it was permissible to do so. I don’t know how many prayers I performed with them. Do I have to make them up?

Ustadh AbdulAziz al-Haqqan

Subhana Allah, don't repeat them but repent to Allah.