It is lawful for you to eat from the food of Christians including the food that they cook on their holidays, except the ones prohibited in the Qur’an.
“This day, all good things have been made lawful to you. The food of those who are given the book is lawful for you and your food is lawful for them. The chaste women, be they either from among the believers or from among those who were given the book before you, provided you become their protectors in wedlock after paying them their bridal-due, rather than go around committing fornication and taking them as secret-companions. All works of those who refuse to follow the way of faith will go waste, and he will be among the utter losers in the hereafter.” (The Feast 5:5)
Celebrating Christmas and celebrating new year are different things. Christmas is a holiday in Christianity. It would not be appropriate for a Muslim to celebrate the holiday of another religion. You can accept the gifts and return the favor with your best wishes. You can pray for them with your own words. There is nothing wrong with these. But you shouldn’t celebrate any holiday of a religion rather than the authentic one.