The general advice is: eat mostly whole foods, not too much, exercise sleep and avoid stress. After that, it’s really up to you to find what foods make you feel better and more satisfied (and of course taste better)
Nutrition science is really hard because people LIE, and all western run studies use self reporting. 'My 600-lb Life' is all you need to know about self reporting.
1) eat food
2) not too much
3) mostly plants
2 and 3 are mostly self-explanatory. 1 is to differentiate between food (things you make yourself or ones with a small number of pronuncible ingredients) from the rest, the vaguely edible processed food-like substances that aren't often good for you.