Does it turn out that the funds of the users are liquid?
Yes, but it’s true only for those who can stake so far. Other users will access transferring and selling tokens at later stages. Exact timeframes are not known so far.
How do block producers work?
These are the subjects responsible for network protection and performing the duties of the pool assigned by a pool chain, they also have a right to manage infrastructure (client-validator) to perform the duties of the pool on the behalf of one of its participants.