@niebing1987
For my poor english, i do not understand clearly ACC and Gyro is in phase,
My English is not good either 
I mean that the Gyro signal (angle variation, deg/s) can be seen as the first derivative of the ACC signal (deg)
Gyro signal should be zero when ACC signal is horizontal (dX/dt=0)
On the first diagram the red curve cross the zero axis when the black curve reaches a max or a min.
This is also noticiable on the left side of your second diagram.
Kalman parameters are specific to sensors type (noise)
Now your filtered angle is much better, but too much filtered
What do you think about that? And in your opinion what baud rate should we use if possible?
I will experiment and be back by the end of the week