"Stepping out to smoke a fag" has totally different meanings in US and UK English.  

A couple of expressions which I've seen in Slovak are nonstop (=open 24hrs) and dres (=a footballer's jersey). My family name sounds like a vulgar word in Slovak, too.  I won't tell the whole story of how I found that out, but just imagine a long, deathly silence followed by gales of laughter.   O_o 

I also discovered, mid-lesson, that žiadný čas (no time) sounds like жадный час to Russian ears: "greedy o'clock"?! :D

The English word 'book' sounds exactly like 'buk' in Polish language, which means the kind of tree:  beech

Comedor, in spanish means something like a dining room, place to eat... in portuguese it means a gentleman who concluded with success a bodily demonstration of affection towards another human being :)

Yes Débora. Smoking means Tuxedo. And I found out it's the same in other Slavic languages and also in German 
https://pl.m.wikipedia.org/wiki/Smoking?wprov=sfla1

BTW. I didn't know it is called tuxedo in English so I had to check it before I commented your discussion  :-)

And just a joke about Polish-English false friends:
- I had to see the dentist while being in UK. I showed him the aching tooth saying 'Tu' (means 'here' in Polish, pronounced like English 'two') and he removed two teeth!
- You should be happy that you didn't say 'Ten' ( means 'This one' in Polish).