Kann Arduino Nano eine Spannung ausgeben?

It certainly does not!

So what made you think of using an LM3914?

Do I presume you want to do this with only one I/O pin?

Eh? How do you propose to count up to 15 objects using 5 LEDs? Binary?

A 74HC4017 will drive 10 LEDs (with resistors) using two I/O pins - count and reset. You just reset it and pulse it a given number of times to select which one of the ten outputs is HIGH.

One or other of the outputs will always be HIGH or you could use the I/O driving the reset line as the common return for the LEDs, using just one resistor to blank all LEDs when held HIGH.