If you know Croatian, you basically know Serbian, Bosnian and Montenegrin. The only difference is sometimes these can be written in Cyrillic like ''мрзим те.'' Also with Persian knowledge you can extend to Tajik and even Pashto or Dari. Same with the Romance languages and Slavic ones. For example if you want to know in Bulgarian it's ''мразя те'' (similarly to Serbo-Croatian) or ''ненавиждам те'' like Polish.
I don't think your Bangladeshi because that's the name for the citizens of Bangladesh and no language there is called like that. Bengali is the actual language of Bangladesh, so therefore I don't think you are a person from there.
