Complex sentence: Colin O'Brady is the current world record holder for the Explorers Grand Slam (Last Degree); he became the fastest person (male) to complete the challenge in 139 days on 27 May 2016.
Split into simpler sentences: Colin O'Brady is the current world speed record holder for completing the Explorers Grand Slam (Last Degree). He became the fastest person (male) to complete the challenge, doing so in 139 days on 27 May 2016.