Hello to you. Congratulations on the trailer.
You probably meant 'food' and the answer is Yes. Just cool down both the fridge and the food before putting food in the trailer.
Fresh water: Some fill at the campground, others fill before they head out. Water is heavy so it can make towing easier without the weight. For some, the position of the water tanks (in front or behind the axle) can make a difference in problems with sway. Either way, if you haven't already, you should sanitize your fresh water system before you use it.
Black tank: It is a good habit to have some water in the bottom of the tank. It helps prevent buildup on the bottom of the tank and the water sloshing around helps clean the tank, too. As far as chemicals in the black tank, some use them and some do not.
Sherm & Terry w/rescues Steve (std Poodle) & Eydie (min Schnauzer)
2015 Jay Flight 27RLS (Camped: 102 nights 2015, 90 nights 2016)
2006 Ford F350 6.0 PSD, Lariat, 4WD, CC, LB, SRW, auto., Camper pkg.