How to stop a leak of water through a concrete floor
The real solution is to prevent water from escaping the pipe by finding and fixing the initial leakage. This will most likely include getting to the upstairs neighbor and kindly asking him to assist with this problem and if he doesn't want to assist bring that to the building management, authorities and the court.

It will be very problematic to seal the ceiling from your apartment. Concrete is not a sealant material - it will absorb and conduct water so water will eventually find its way to your apartment. So this would be just a waster of time.