work (okay AUX & SD, USB not detected, no display, volume difference) with restrictions

The box is connected to a radio RD4-N2 in a Peugeot 207 BJ 2006: After driving to the workshop and unlock the CD changer input AUX input is working properly, SD works with limitation (long time to read, sometimes crashes), USB from functioning not (different USB flash drives with sizes ranging from 512MB to 8GB tested).
Unfortunately, I have no CD / title number. In the display and must flying blind control (not only no name / day, but no display on the screen). Also, the volume setting is not shown on the display. Disturbing is the volume difference between Box and Radio, so you absolutely should turn the volume down again transferred from Box to Radio.