Who should I ask to repair the leak in the bathroom? How to deal with water seepage in the toilet?

The toilet leaks, so you need to contact the property department for maintenance.

The property department will contact the construction unit for warranty, because the developer has signed a contract with the construction unit and deducted the cost from the deposit of the construction unit.

There are several ways to deal with toilet leakage:

After the toilet is waterproof, it is best not to use it immediately. It's best to leave it for a few days or even longer to make the decoration stronger, so you don't have to worry about it in the future.

The waterproof layer is the part prone to problems, and the root of the problem must be found first. If it's caused by water leakage, that's good. Just buy waterproof coating, with 2 to 3 layers on the surface, and then use it after the waterproof layer is completely dry.