All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If the talking about permissible topics related to worldly matters in the mosque is free from raising the voice and disturbing the worshipers, then there is nothing wrong with it, Allah willing.
Imam An-Nawawi said in al-Majmoo’: “It is permissible to talk about what is permissible and worldly matters in the mosque and other permissible matters even if there is laughter and the like as long as the talk is permissible, as Jaabir Ibn Samrah, may Allah be pleased with him, narrated: “The Prophet did not stand up (and go) from the place where he offered the Fajr Prayer until the sun rose, and after the rising of the sun, he would stand up. [Jaabir said] They [the companions] used to talk about the stories of the pre-Islamic era, and they would laugh, and the Prophet would smile.” [Muslim]
However, some jurists are of the view that talking about worldly matters in mosques is disliked.
Ibn Muflih al-Hanbali, from the Hanbali School of jurisprudence, said in his book Al-Adaab ash-Shar’iyyah:
“It is Sunnah to protect the mosque from useless and idle talk, and raising the voice with what is disliked; this implies that it is not disliked if the talk is permissible or desirable, and this is the view of Abu Haneefah and Ash-Shaafi'i ....... Abu Abdullah ibn Battah - – said: “It is a Sunnah to mention Allah and speak about (Islamic) knowledge in the mosque, and to avoid indulging in useless and idle talk and speaking about worldly matters in it, as this is disliked. Many threatening and difficult narrations have been narrated with sound and authentic sources and trustworthy men, among which is what was narrated from ‘Abdullah ibn Mas’ood that the Prophet said: “At the end of times, people will sit in mosques while their only purpose is worldly matters; so do not sit with them, for Allah has nothing to do with them.”
Among these narrations also is the narration on the authority of ‘Abdullah ibn ‘Umar who narrated that the Prophet said: “The Hour will not come until people will sit in the mosques and there is no believer amongst them; their talk in it is about the world (i.e. worldly matters).”
Allah knows best.