You need to make sure the hot wire is switched off. That does matter.
In the US single pole light switches go on the hot line. If you do it the other way around it's against code. You can be shocked if it's done backwards and your changing the bulb.
Repeat after me: in Europe, the polarity is not enforced by the plugs, so every device with a plug
must be made to be safe regardless of polarity. This is why in Europe, devices with plugs must be double-insulated. (The only way a device can be sure of polarity is to be hard-wired.)
The OP is in Bulgaria, which is part of Europe which uses the German-style socket, which does not enforce polarity even for grounded plugs. So any appliance used there MUST be designed to be safe with either polarity.
For all intents and purposes, the Americas are the only place that still relies on polarized 2-prong AC plugs for safety in any way. (I suppose the Australian plug enforces polarity, not sure if they allow devices to rely on it, though.) But since more and more products are designed for world compliance anyway, they just properly double-insulate anyway.
And why are you even bringing up light switches and sockets? We aren't talking about house wiring, where things must be done accurately. This is a plug-in device, which must comply with different standards separate from household code.