Thank you garcia! Well first i would recommend you to take a look at Substance designer/Painter to get you started in the texturing process. Secondly, practice your lighting skills, look at how real-life light works and try to redo it in-engine as good as you can. Thirdly when you need to create foliage i would recommend you take a look at SpeedTree it’ll make your life much easier. And fourthly PRACTICE!
I hope this helped you a bit GOOD LUCK 