My Arduino Nano project contains two 5V servos (MG90S) of which the datasheet does not mention current, a 5V LCD with a max current of 8mA, a 5V dc motor in a waterpump with max current 200mA and some sensors. Can I just power the sensors from the nano and do I need a separate 5V supply with like 2 Amps to power this?
The servos and pump will only be rotating for a few seconds per hour. And it is possible not to rotate them at the same time if that helps.

I hope someone can tell me how to properly power my idea. THANKS A LOT!

 

When you refer to model servos (which I assume you are), the brand and type (digital or analog) make a difference. Current is infrequently given, as it varies substantially with load. However, current does increase with the servo torque rating. A servo rated at 300 oz-in will draw a lot more current at its maximum than a servo rated at 30 oz-in. As an example, a typical 3-m glider with 4 miniature servos in the wing and 6 servos total can draw in excess of 6 A when those servos are working had.

For your set-up, I would definitely use a separate supply for the servos and probably water pump too. The LCD (without backlight) and sensors are probably OK being driven from the nano, but the datasheets for the sensors should be consulted.