research

research functions differently than "istraživanje".  While it is a noun, i.e. you can "do research", you can't call the final result a research or "researches".  You can have a "research report" or "research results" or an "[academic] paper".

medicaments

Yes, this word exists.  No we hardly ever use it.  Medicines is perfectly fine

jedinstven

= unique in the sense that there is only one like it
= unified in the sense that it is integrated i.e. part of one whole

relations(hips)

countries have relations, you can study international relations.  But to my ear when you say that people have relations it sounds a bit like THAT kind of relations.  Relationships is safer and better to my ear.

Prepositionally

This text is written in English. (read period).  Not on English.  And not "on the English language".  Here's one where English is simple and to the point.  Just start with in.  And you translate "into English", "into Bosnian", etc.

The simple past

I don't know if I'm just a stickler about this, but I constantly change "was spending" to "spent", "were going" to "went", and so on.  I have a theory that because in B/C/S you say "isao sam" that it just seems natural for people to write a compound form for the past.  This is another one of my top 10 things I'd drill into every English learner.

Realizing manifestations

These are at the top of my list -

• Plans are implemented, not realized (I just realized this!)
• Large groups of people gather together to demonstrate and hold a demonstration not a manifestation (this is manifest!)
• Only in SEE is a political gathering a meeting (miting).  I suppose this was a foreign idea, but we foreigners would call this a demonstration, too.
• Events can be current, the latest, and the newest.  But actually events like this can not be actual.