Making an automatic night light
I want to design a circuit and I'm stuck.

Yeah well, like many, many "aspiring circuit designers" have experienced before you, it is nearly impossible to do circuit design without knowing how certain circuits are build up. Yes, a MOSFET can act as a switch and yes a resistor can limit a current but knowing that is not enough.

For example, for an NMOS to act as a switch its gate-source voltage needs to be switched between for example 0 V (off) and 5 V (on). In your circuit the 5 V for on/off sits between the gate and something that is not the source.

I strongly advise you to search the internet and look for circuits which do the same. "NMOS switch circuit" should be a good start. Use the "images" tab to see pictures of schematics. Not how many are similar. Then build something similar in LTspice and experiment with it.

To learn how to properly design circuits I would recommend looking at circuits a lot and figure out what makes them tick. Re-build circuits in a simulator and make small modifications then think what effect that will have and then confirm that using the simulator. If you like that and gain more experience with that you can become an excellent circuit designer.

If you just want the night light function and don't aspire a career in electronics ( :-( but your choice) then don't try to design a circuit yourself, it will end in tears. Just browse the internet for similar projects and copy that. Circuit design isn't something you can learn quickly to make a circuit you suddenly need. The hard work has been done already by others so just copy what they did.