Quale lampadina va nel mio attacco e quanti lumen mi servono?

The socket decides which bulb fits. E27 is the large screw socket and E14 the small one (Milieu Centraal). GU10 has two pins with thick heads that you twist in, G9 two loops that you push in, GU5.3 two thin pins for 12 volts. If in doubt, look at your old bulb: it says so on it.

How much light you need is measured in lux: lumens per square metre (licht.de). Licht.de advises at least 500 lux in the kitchen, at least 300 in the bathroom and 300 to 500 in a study, with 500 for a real home office. We calculate 500, 300 and 500 lux times your m². For a living room licht.de gives no lux, but 3 to 5 lamps for 20 m², at different heights: we count 4 per 20 m².

This is a rough estimate: a shade or a dark wall swallows light, so take a little more and dimmable. An old 60 watt bulb gave about 800 lumens. Below are LED bulbs with your socket and at least 200 lumens, cheapest first; we read the lumens from the product data.