I've got 2 questions left:
can I use the capacitors in a breadboard like this (imagine the resistor would be a capacitor):

Do I have to care about the rating of a capacitor, because
this one has a rating of 50V
and I would use
this to connect my adapter with the circuit. But Im wondering what is + and - there, and can I just put the - straight into the ground of this component?
A little question I have as well is wether I need adjust my arduino for the power supply at the 5V pin.