Have you seen my first Circuit? Well, I'm a beginner and I've made a very amateur mistake. Have you known that it was not a good idea to connect a GPIO out to the GND without any consumer? Well a MOSFET is not a consumer.
I connected my GPIO to the MOSFET. I measured the running current, and it was 35mA. I thought it is not a lot and it should be fine. So I short (is this the right word?) my GPIOs even though for only a very short moment (0.01 sec) at a time. What has happened? I noticed nothing. It worked well, and the notifications system made beautiful sounds. But later I run into a problem: the Pi was not working as expected. There were more and more error messages. About corrupted files. I had to recreate my whole system.
So shorting your GPIOs for a very short time does not necessarily kills the Pi, but destroys your system step by step. One easy solution is to put a 330 Ohm resistor between the MOSFET and the Pi.