Hello, thanks to everyone for the qiuck replies... I am a bit slowlier and it took me a while to find a solution...I thought it is about the code... but it is not! It is right the H-bridge, which really takes away plenty of energy and this is why the motor does not see the whole voltage... And by increasing the supply to h-bridge it also makes the motor run faster almost at maximum speed. I did not try mosfet but - yes it would probably also help.
I am already happy now 