Complex sentence: Isfahan is the host of many national and international sport events therefore enjoying sport facilities such as Naghsh-e-Jahan Stadium with 50,000 capacity which second phase is under development to increase capacity to 75,000 spectators.
Split into simpler sentences: Isfahan is the host of many national and international sport events, therefore enjoying sport facilities such as Naghsh-e-Jahan Stadium with 50,000 capacity. A second phase is under development to increase its capacity to 75,000 spectators.