Sewer smell in Bathroom - PLUMBING CODE - P TRAP ??

mild sewer gas like smell in my bathroom. Toilet has water in it so no gas from there.

My question is regarding the Sink and bathtub " P-traps" what is the plumbing code in Poland regarding these? any links with photos you can provide? Looking at my sink trap It looks like no complete water barrier so that may be the problem. Bath venting appears to be correct.

Also what kind of plastic is the white drain plastic? I'm curious - north american standard for drains is black ABS

If there's no water barrier then you've got a faulty bog and need to get a plumber in. All toilets here have a water trap.

is there a drain in the floor ? sometimes they're tucked into the corner and dry out if you don't know to top them up with water from time to time.

Yup I had the same problem in one of my ground floor place,it stinks when the toilets etc are not used over a period of time so if you let the water run a while the smell goes away.