any tips to play ?

Glad to see new people playing ES1. Here's some general advice.

The game can feel a bit overwhelming at first, so make sure you haven't activated the Disharmony DLC. If I remember correctly, you can activate/deactivate the dlc from the main menu. 

Feel free to take your time discovering the lore and understanding the mechanics.

Lastly, some factions have different game mechanics, so you should avoid playing the more unique factions. I haven't played ES1 in a while, but I recall these factions to be more difficult to learn: The Cravers, Hissho, Sowers, Automatons.

As another new player I have two questions about the game:

What advantage gives a high food production in a system, if it is already on maximum population? Or is there none and I should sell all the improvements for food production?

Most of the upgrades say +x planet and also +x planet-type (like desert). Does that mean every planet gets the +x planet bonus and the bonus for its type on top? Also, do asteroids count as plantes?