Is it permissible to demand money from a partner in a commercial project, knowing that he is procrastinating in paying what he owes and claiming the project is ongoing, while there are doubts about that?

There is no harm in requesting the agreed-upon profits if you both consent to them. The partner's statement regarding the profit's occurrence is sufficient. Profit is only realized after the safety of the capital is ensured. If no profit is made, you receive nothing. If a loss occurs, it is borne by the capital, and the partner is not liable for it unless there is negligence or transgression on their part. It is permissible to divide apparent profit on account, and the final profit calculation is re-evaluated after the capital has been recovered. Once profit is realized, it is distributed between the two parties according to the agreement.