Croatian won't help you ordering food in Poland.
The names of the basic food like milk, potatoes, tomatoes and so on... are in the most cases very similar (proto-Slavic roots), but for cousin it is not the case... there was obviously split between Poles and Croats before our present cousine customs are made.
We have more similar cosine names with Hungarian and surprisingly with Romania than to Polish and Slovakian.
This is the most similar language to Hungarian:
https://www.youtube.com/watch?v=QddPWzD_alk
I asked my Hungarian friend and he didn't understund even a word
So, all the Slavic languages are more similar to each other than this language is similar to Hungarian.
Probably even Baltic languages are more similar to Croatian than Hungarian and Mansi.
And SLavic languages are more similar to each other than German and English.
We can understand Slovak and Czech more easily in the written form; because the similarity of the words are more recognizable, and we use very similar letters and the rules of writting are very similar.
But Poles have very different writing sistem, they have lot of letters we don't have and different rules of spelling
Same like Croats and Serbs
Which language did you speak?
Every language has specific pronunciation, so native speakers are usually easily recognizable when they speak some foreign language.
So you will have problems hiding it even if you speak Croatian in Slovakia.
Maybe in the USA nobody would recognize you are Hungarian, because they don't know Hungarians, but in Slovakia it is different case.
Like we recognize Slovenians, Italians, Germans or Turks when they speak English.
there is no point of learn Croatian if you want to use it in Slovakia and Poland.
Like there is no point of learning Spanish if you want better communication in Philippines, just because you like Portugal or/and Portuguese people.
And I doubt about learning Slovak or Polish will help you to hide your Hungarian nationality.
Kurva/kurwa is not a false friend in Polish and Croatian. They are synonyms. Like in Croatian and Hungarian.
The meaning is whore in all there languages.
But Hungarians use this word more, in different contexts, and Poles even more
SO, the meaning is whore in polish.
Usually in the ENglish texts they translate the meaning of kurwa in wrong way. It is not "fuck". It can be translated in some contexts like fuck, or shitk, or what a fuck, or fuck it, or god dammit, or motherfucker, or yo,or just skip it, when Poles use kurwa in stead of comma in the sentence. Some Poles do it.
.
But the basic meaning is still whore.
Smae like suka in Russian, Ukrainian and Hungarian.
SO, kurwa can be translated in Croatian like jebote, jebi ga, u p... m...., eh, ah, not just kurva .
The real false friend of Serbo-Croatian/Macedonian/Bulgarian/Polish/Hungarian/Slovenian kurva/kurwa/kurba is Italian curva, which is pronaunced complitly the same like in Croatan and Polish, but it means curvation .
So fale friend between Polish and Croatian are not so common (like in Croatian and Slovenian for example) and they are not the problem.
The problem is that Croatian and Polish & Slovak have different grammar endings/changes of the word, different pronunciation and accents, so even the word are similar to some extent, it is hardly recognizable, even for native speakers.
And maybe the most important to you; you won't be able to hide that you are Hungarian to Slovaks even if you speak Croatian, like you can't hide it when you speak English or German.
And about swearing words in Croatia, Bosnia, Montenegro and Serbia; we are very creative about that; there are numerous swearing words and even more combination you can even imagine. And we occasionally create some individually. Just don't try to translate it.