The diet of choice for many in Crossfit is paleo. If you don’t know what to pick try it.
Others (including myself) is not that strict and eats some that is not included there (like milk, some grains and so on), but most good diets for health and training are similar. Eat enough good protein, good fat and more vegetables than you think you need.
If you really want to go all in check Zone too.
There are a lot of good answers in this subforum and in the beginners subforum.
And have fun! No one eats perfect!
And welcome to the forum! Nice to see someone from close by.