I have a new bike for 3 month and after about 20 Km my ring and index finger on the left hand became numb. Just as an information for my hand position: These fingers are always on the brakes. Here is my handlebar and brake lever position. Any idea how to adjust them to get rid of this problem?
There is nothing obviously wrong with your handlebar setup. As long the shift and brake levers are easily accessible and you don't have to rotate your wrists or shift your hand laterally along the bar to reach them everything is OK
Maybe I'd consider moving the levers slightly outwards (and I note there is a slight difference in position, the right hand one is slightly more inboard.
Numb hands are a common problem. You don't have to ride with your fingers on the levers all the time. Try moving you hands around the bars and bar ends and flexing your fingers from time to time.