Is it permissible to hold wedding celebrations with drums and dancing in a hall beneath the mosque, designated for resolving people's issues?

If the hall was not intended by the builder to be a mosque, then there is no harm in gathering in it to resolve worldly issues, hold celebrations, and rent it out, with the prohibition of using drums and musical instruments except for the daff (frame drum). The prohibition is emphasized because it is located beneath a mosque.

However, if the hall is included in what the endower intended as part of the mosque, then it must be protected from worldly matters, and selling and buying are forbidden within it; because Allah the Almighty says: "In houses [i.e., mosques] which Allah has ordered to be raised and that His name be mentioned therein." And the Prophet (peace and blessings of Allah be upon him) forbade selling, buying, announcing lost items, and reciting poetry in the mosque, and he informed that mosques were not built for that purpose. It is permissible to perform marriage ceremonies in the mosque while avoiding reprehensible acts.