Nutrition

For months i've been trying to improve my skin quality, i've tried skincare product and they did not work, and only recently i've understood that the only way to tackle this problem is to solve it from the root: my nutrition. I don't want general advice like "start keto" or something like that, i'm open to discuss proper scientific evidence on why some foods are good/bad. Here's some question we can start debating on:

1) are veggies actually that bad?

2)What's the difference between complex and simple carbohydrates, and how are they abbsorbed?

3)how does nutrients abbsortion works? And what is the ideal way they can be absorbed?

4)is eating a lot of meat actually useful?

I hope to recevie useful information so they can be helpful both to me and the people with my same problem