I improved the ground plate, that you can use the 28BYJ-48 stepper motor to rotate the whole arm.
To controll the servos i used an Arduino UNO with the adafruit 16-channel PWM-Shield: https://www.adafruit.com/product/1411
And to controll the stepper-motor, i used as normal ULN-2003 darlingon-array.
The small "Table", which holds the whole construction in place, i fixed on a board of wood with hot glue.
This is a remix of: https://www.thingiverse.com/thing:907281
Printer: Prusa i3 MK2S