AhsanAllahu ileikum, my imam just started reciting surah kahf 10 minutes before the jumua adhan. The last time they gave some speech 10 min before jumua adhan. Is this bidah, should i listen or do something else. JazakAllah khayr

Your Imam shouldn't even pray tahyat almasjid, and he should instantly go to the minbar gives salam and sits, listens to the athan, then does the khutbah. Then he can teach after the salah just like how our sheikh Muhammad Hisham does.