أحسن الله إليكم شيخنا Should I pray separately with my friends who are upon the Sunnah (إن شاء الله), or pray in a masjid with 15–20 people who commit various bid‘ah and make mistakes in ṣalāh — e.g, always saying takbir after getting up from sujūd instead of while getting up? جزاك الله خيراً

Ustadh AbdulAziz al-Haqqan

Pray in the masjid, and the prayer is correct as long as it is valid for the imam. If his prayer is valid, then yours is valid, provided they do not commit bid'ahs that are kufr bid'ahs.