Hello friend I really need to change the language of my panel but I've spent hours trying and I can not. Can someone please help?

fullcalendar.js https://drive.google.com/open?id=1xktFUmkxgbzxLwVnCdZOFlsyHmmccPvW

Page that loads calendar

manage_holiday.php https://drive.google.com/open?id=1IL7eNKh1c7h_qQNGbzgC0zLB-HgvB3Ya