What is the ruling on building a mosque with two floors, where the first floor is used for holding wedding parties with Western and Indonesian music and singing, and the intermingling of men and women, without observing prayer times, while the second floor is a mosque?

There is no harm in having a two-story mosque when needed, but it must be protected from all sin and evil. What was mentioned in the question about frivolous activities and loud celebrations inside the mosque is a grave evil and a desecration of the House of Allah. Islamic law has forbidden mere commotion and raising voices within it, so how much more so the mentioned evils? It is incumbent upon Muslims to denounce and change this evil. The first floor should be used for prayer, and if the second floor is sufficient for prayer, then the first can be used for memorizing the Quran and teaching Islamic sciences.