Philipp1202:
The voltage I give are the 5V of my Arduino Mega 2560 board, might this be too low
It will be a lack of current, not voltage, although I'm not sure why it would work for a little while.
You need a power supply external from the Mega, as shown.
edit: According to this, those serovs can draw 750mA, so if all 5 can move at once, you need to provide about 4A.