I took all your advices serious and started over again. By chance I got on weekend from AliExpress a strong hand vacuum pump
(Link). I closed with the hand the tank on the handlebar and created a strong (!) vacuum in the brake system. By that means the last, hidden and sticking small air bubbles became bigger and moved inside the system. When quickly released the hand from the tank I created a kind of hydraulic shockwave. It blew out the last air bubbles.
It works now like a beauty, better then ever.
Thanks to all
Cheers Joa
