Did Friedmann by his equations find a problem in the theory of general relativity? Because at first Einstien built his theory on a steady state universe. But, Friedmann according to this theory estimated that universe cannot be in the steady state and should expand. If yes, what was the problem of the theory with the steady state?
When Einstein developed GR, cosmologists did indeed believe the Universe existed in a steady state.
However, Friedmann found that GR only works if the Universe is either constantly expanding or contracting. To force the field equations of GR to spit out a steady state universe, Einstein added the cosmological constant $\Lambda$ to the equations.
This term was then removed when the expansion of the Universe was discovered by Hubble and others, and then added again very recently (but acting repulsively rather than attractively) after the expansion of the Universe was found to be accelerating (aka dark energy).