…steeper ascents like couliars >40° are hard and I am fare above aerobic zones being as fast as my colleagues.
It’s probably not a valid comparison. If your colleagues are typical climbers, they are probably well above their aerobic threshold, likely anaerobic.
What specific training can make me better for that? Muscle endurance? Strength training?
More of the same. And strength. Base aerobic capacity is always “more is better”. Strength training will help and judicious use of muscular endurance training.