Hello from cold Russia.
1)Don't use the grounding wire to connect N pin on your wall switch. If you don't want to win Darwin award.
Look at the first picture.
2)Use capasitors to connect the switch and the bulb.
Look at the second picture.
C1 - Capacity. Metal-film capacitor for 400 volts.
It works as a "quenching capacitor" or "resistance". In order for the "part of the current" to remain on the switch and feed it, in the switched on position of the key.
C2 - Capacity. Metal-film capacitor for 400 volts.
Works as a "bypass" resistor. Serves to ensure that energy-saving gas-discharge or LED lamps do not blink (from the current passing through them supplying the switch) in the off position of the key.
To Marius Herta.
You used 4.7 uF capacity as C1.
What kind of bulb did you use? It seems to me it is a gas bulb. Which is about 10-15 Watts.
I guess - you've got to use 2,2 uF capacity in case that is 15 Watt bulb not 4.7.
Use the rigth capacity.
2. I do not see C2 on video. There is no C2 in the wiring of the bulb.
Install the C2 capacity to ensure the bulb not to blink in the OFF position of the wall switch.
I have setup three Sonoff 2nd gen switches. With different capacitors, basically I have two switches with C1 being 1uF, one 1.5uF. One LED bulb C2 is 0.47uF, without it it flickers. For second switch I have two LEDs with C2 being 1uF. To avoid weird glitches, like one lamp not turning on or one flickering other not, I have to use both LEDs same brand same wattage. Last interesting thing is that Ikea LEDs don't need C2, since they don't flicker.
So in general all works like charm, but there is two bugs. One is phantom clicks - sometimes light turn on by itself and it is happening randomly with all three switches. I don't know if it is related to this type of connection with capacitors or it is some bug with Sonoff switches. Another bug I noticed is that switches sometimes randomly goes into pairing mode for about 5 min, then connects back to WiFi.
Anyone have experienced this kind of bugs?