Complex sentence: Guillermo Salinas Pliego, head of AVALANZ, promised to finish the project in 300 days, he added "It looks difficult but, the Monterrey Arena was the same and it was finished in nine months".
Split into simpler sentences: Guillermo Salinas Pliego, head of AVALANZ, promised to finish the project in 300 days. He added "It looks difficult but, the Monterrey Arena was the same and it was finished in nine months".