Is it permissible for a father to close a mosque he built on his land and convert it to another activity, or leave it closed, or close it and donate part of the money to another mosque, or donate an amount to build another mosque, given the presence of many mosques around it, the small number of worshippers, the abundance of problems within it, and the uncle's attempt to seize it?

He who builds a mosque and opens it to the public, it becomes an endowment (waqf) which cannot be sold or closed. An endowment is a binding contract merely by declaration, and it is impermissible to revoke or sell it, unless its benefits are completely lost. If its benefits are lost, then it is sold, and its price is spent on something similar. One must advise whoever claims ownership of the mosque by explaining that it is not owned by anyone, and encourage people to perform congregational prayers, presenting the most knowledgeable in recitation and the most jurisprudent for leading the prayer.