What is the ruling on establishing mixed wedding halls connected to the mosque, and do you advise us to sever ties with this mosque?

A wedding hall should not be attached to a mosque if it involves intermingling (of sexes), music, and disturbance to those praying. The presence of women in the mosque adorned and without hijab during prayer times is a great reprehensible act (munkar). Those in charge of the mosque must fear Allah, and they should be advised gently and wisely. If they persist in this reprehensible act, then abandon this mosque and pray in another mosque.