dificulty

[rui]

Game is extremely dificult, the moment you leave skyranger you always get atacked.

Make enemies a bit easier to kill, even after beginner level game gets impossible to play.

[Xilmi]

I recommend using my Brutal-AI-Mod, which you can get here:
https://github.com/Xilmi/OpenXcom/releases
and setting the difficulty to Superhuman.

Obviously not because that would make the game easier but because after playing for a while with that, you will perceive the base-game on beginner-difficulty as a lot easier in comparison.

It would basically be a way to re-calibrate your perception of what is difficult and what is not. Similarly to how you can overcome the addiction of highly processed food with lots of salt, fat and sugar by eating just vegetables for a while so that even fruit will be perceived as delicious.

If you want to learn more about the biological backgrounds of the perceptual re-calibration, you can check out "The pleasure trap" by Doug Lisle.

[Varana]

I think genius is the easiest level. On beginner levels you simply don't have enough income to get things better in time.
And you do not have to leave the vehicle in your first turn, when aliens are waiting on alert and have not moved yet...

There is a very good and simple mod for beginners, "lost war", that introduces some of the game basics:
https://openxcom.org/forum/index.php/topic,9053.msg135490.html#msg135490