Is it permissible for the second party to insist on the verbal agreement of paying annual installments or selling the properties on the basis that their share equals half, while settling the remaining debt to the first party, given that the first party wishes to terminate the annual payment agreement and sell the property now?

If the two partners have agreed to pay the share of one partner in the construction financing in installments, then this partner is not obligated to expedite the payment of his installments or to sell the building and land, unless they mutually agree otherwise. This is the preferred view in the Maliki madhhab (definition), as they hold that postponing the repayment of a loan is binding if it is specified at the time of the contract; otherwise, it is determined by custom. This is also the view preferred by Sheikh al-Islam Ibn Taymiyyah, who cited the hadith (definition): "Muslims are bound by their conditions."