Alfadiag, re-calibrate your system and chances are your clutch is wearing and may need adjusting, People lets not forget this is a manual gearbox with a robotic clutch. If you think along the lines of this you will find the fault is quite simple(hopefully) it could also be a small leak on you actuator but try everything else first.
1, selespeed oil level?
2, gearbox oil?
\but by the sound of what you say i would say clutch needs adjusting. (this is not gospel as i am still learning, but these are the basics to check)