Inserting Serbian Latin and Cyrillic characters
You have to specify that you are inserting wide character data:

CREATE TABLE #t (id INT,c1 VARCHAR(MAX),c2 NVARCHAR(MAX));
INSERT INTO #t VALUES(1,'žđšćč žđćčžđšćčŽĐŠĆČ','žđšćč žđćčžđšćčŽĐŠĆČ');
INSERT INTO #t VALUES(2,N'žđšćč žđćčžđšćčŽĐŠĆČ',N'žđšćč žđćčžđšćčŽĐŠĆČ');
SELECT * FROM #t;
DROP TABLE #t;


Result: