If your bathroom faucet leaks between the nut and the gooseneck, most probably the o-ring seals are damaged.
It’s not uncommon in Eastern Europe to use one faucet for both bath and sink, for economy. And this is in fact much more convenient than that modern low-rise faucets trend which you can’t even place your face under for a proper wash, let alone wash and rinse your hair while standing fully dressed outside the bath and pivoting your head into it. So this European economy has a right to live. The biggest problem here is that the sink overlaps the bath a little bit, to make the gooseneck shorter. If it doesn’t, the gooseneck has to be quite long, about 40 cm. And since it is constantly turned around to face sink and bath, the o-rings get trashed real quick. The easiest way to fix a leak is to replace the inlay seals assembly. It consists of 3 rubber o-rings, a plastic washer which allows the gooseneck to turn smoothly and the threaded tube the seals seat on. So a leak basically means either one of the o-rings or the plastic washer is worn down. As for the repair practicability, the o-rings comprise 20 percent of the assembly cost, the plastic ring is another 30 percent, and whole new gooseneck is 300 percent the cost of the inlay assembly. To unscrew the inlay you will need a 10mm hexagon bit. Apply a little thread locking fluid to prevent it from unscrewing. If you don’t have it, a little nail polish or just a tiny drop of superglue will do. When you have to unscrew it again, use WD-40 to dissolve the cured glue.