Complex sentence: Banjoist Marko Čermak built the first true Czech five-string banjo from photographs taken at the concert, and soon after started playing with the group Greenhorns or Zelenáčí.
Split into simpler sentences: Banjoist Marko Čermak was able to build the first Czech five-string banjo from photographs taken at this event. Soon after he started playing with the group Greenhorns or Zelenáčí.