Complex sentence: The NFL will play one game at Estadio Azteca in Mexico City in 2018, in accordance with an agreement the league announced in November 2017 to play one game at that venue each year through 2021.
Split into simpler sentences: The NFL will host a game at Estadio Azteca in Mexico City in 2018. In November 2017, the league announced an agreement to play one game at that venue each year through 2021.