Complex sentence: The German ships began picking up British MTBs on radar around two hours after midnight on 13 May and crew on some of the German ships reported hearing motor noises, but the MTBs could not be seen.
Split into simpler sentences: The German ships began picking up British MTBs on radar around two hours after midnight on 13 May. Crew on some of the German ships reported hearing motor noises, but the MTBs could not be seen.