Complex sentence: Of the numerous races held in 1937, only the Belgian, German, Monaco, Swiss and Italian Grands Prix counted towards the championship but the French, Czech and British races were significant events and worth including.
Split into simpler sentences: Of the numerous races held in 1937, only five, the Belgian, German, Monaco, Swiss and Italian Grands Prix counted towards the championship. The French, Czech and British races were also significant events and worth including.