Complex sentence: Hernán Vivanco joined the club as the coach and began getting the players to play an exciting game of football and alongside a strong advertisement campaign Salvadorans (in particular San Salvador residents) began to change their allegiance from Juventud Olímpica and began to embrace Alianza.
Split into simpler sentences: Hernán Vivanco joined the club as the coach and began getting the players to play an exciting game of football. Alongside a strong advertisement campaign Salvadorans (in particular San Salvador residents) began to change their allegiance from Juventud Olímpica and began to embrace Alianza.