>>217203586
Bulgarian is most similar vocabulary wise though its grammar is different so it sounds "weird" (but generally understandable).
Slovene sounds like a bit corrupt Serbian, especially that Serbo-Croatian itself is divided into many dialects and some are very close to Slovene, it's generally one dialectal continuum all the way from Triglav to Vranje. Also Slovene borrowed a lot of phrases from Serbian, basically all swear words in Slovene are Serbian in origin.
Czech(oslovak) feels like "a more distant Slovene", orthography is quite similar though vocabulary wise it's rather different.
Russian has a lot in common with Serbian due to common Church Slavonic heritage (many similar words) + in 19th century Russian language had a profound influence on Serbian (+ Serbs use the same alphabet).
Polish is the least similar and least understandable, it sounds like "pshshshsch" to them.

>>217204087
Since slovene IS quite Close to czech/slovak how understandeble To a pole?

>>217204243
at this point it's even hard to say it for me since I learnt Serbian and I naturally understand it better than Slovene so I can't make an honest comparison.
Slovene spelling is so similar to Czech that most people here would probably think a text in Slovene is just in Czech (especially that we have almost no exposure to Slovene here) but the devil is in details, Slovene vocabulary can be quite different, especially when it comes to "bottom high" as well as "bottom low" register of the language in which Slovene borrowed more from Serbian while Czech has its own vocabulary base. But for regular conversation I think Slovene and Czech are fairly similar, though obviously Slovene exhibits also some typical Balkan features Czech doesn't have (they usually don't make the text unintelligible, tho).

>>217203586
idk

>>217204087
>basically all swear words in Slovene are Serbian in origin.
still, a Slovene will say 'pizda materina' , not 'jebem ti majku u pićku' or 'jebem ti oca'
and one might argue that Slovene in fact is Serbian, but as spoken by real Slavs, not 80 IQ arabized Romanians