Power supply voltage amperage?

I have einigr devices without power supply (eg Nintendo Swtich, Gopro). Must the current and voltage of the power supply exactly match the values required by the device, or what happens if the power supply more or less power or volts delivers (eg device wants 5v 2a, power supply 5v 3a, or 5v 1a, or other voltage so 3v 2a or 7v 3a).

One more question… What voltage and current does my power supply have, there are 2 voltages and currents (probably due to fast charge function)

So casually explained:
You can imagine the voltage (volts) like the pressure at a water pipe;

if the pressure is too high, something can break, so the voltage should not be higher than the device has specified.

The current (ampere) is the amount of water that has to flow for the device to be powered. Since the device itself takes the amount of water, you can also take a power supply here, which can provide more "amps". The consumer only takes the amount of ampere it needs.
So; Voltage of the power supply / your power source should be correct, amperage can be quiet, lower would be unfavorable, since the device then may not work properly - because too little "juice" is delivered.

Hope I have you some. Well explained.

Thank you for your vivid explanation 👌 What about a power supply that has less volts than needed?

That For e.g. A Nintendo Switch on the 15v 2.6A is forced I need a 15v power supply so 5v 2.6a is not or 9v 1.8a?

No, the device would not work in this case, because your power supply would indeed deliver "too little pressure". The voltage should be correct, minimal deviations are negligible (1-2 volts more or less), but at 5v or 9v this would definitely be too low.