Complex sentence: The Sardegna Arena is a provisional football stadium under construction in Cagliari, Sardinia, Italy, and will host Cagliari Calcio football matches from 2017--18, since Stadio Sant'Elia was closed and demolished in order to build a new stadium.
Split into simpler sentences: The Sardegna Arena is a provisional football stadium in Cagliari, Sardinia, Italy. Built in 2017, it hosts Cagliari Calcio football matches from 2017--18, since Stadio Sant'Elia was closed and demolished in order to build a new stadium.