Complex sentence: The cave was discovered by a local man in 2005 and 5 first km of this cave was explored by explorers from British Cave Research Association in 2005, the whole 31 km was explored and publicly announced by the British cave explorers.
Split into simpler sentences: The cave was discovered by a local man in 2005. The first 5 km of this cave was explored by explorers from the British Cave Research Association in 2005--the whole 31 km was explored and publicly announced by the British cave explorers.