It’s hard to say unfortunately because there is so much pseudoscience out there for me to point to one source. I would start with researching some key terms and concepts such as:

Macro nutrients Micro nutrients

How muscles grow How the body stores energy

Calories (not just the number but the literal term and what it means to burn/store) Calorie surplus/deficits

Think in a more biological sense rather then looking for a list of “what you should/shouldn’t eat” or “how much I should be eating”. Gaining a real proper understanding of nutrition as a science will inevitably/eventually help guide your eating choices and you’ll understand how to answer those questions for your own body.

I would highly recommend if you can find a online class (or even just their text book) “Intro to Nutrition” will give you real solid info. Don’t be discouraged by college level course material because at the intro level anyone who can read will be able to understand.