In my opinion, the construction is by no means lost yet. As long as there is no roof on, you cannot judge whether the basement is watertight or leaking, and with this weather, all sorts of things quickly grow on the walls. This is also not the first shell construction with a crack in the ceiling. It is important now to continue building quickly, put the roof on, and let it dry. If the basement is really leaking --> seal the basement. I feel sorry for the actual builders, young families who wanted a nice house. Now everything is falling apart for nothing and again nothing. One day you will blame yourself for focusing not on completion but on the legal dispute. Have fun when in 10 years the grandchildren ask and you can answer: there is no house for you, your inheritance is gone too, but we fought a pointless legal battle until the "final victory." By now, there could already be masons at work again completing the upper floor... The loan is available. Okay, it now only lasts until the shell house stage, but the rest you will manage with combined efforts and a lot of personal work. Put your energy into that. You want to make things right? Then buy a Kärcher water vacuum, go to the construction site, and dry out the basement. That way you have made a meaningful contribution.