Decrypt the code in Croatian and specify the key K = (s, b) if you know that Cesar's key code with the key K was used to encrypt (use the instruction that the keyword is a name of a European country). Write also the intermediate steps.
ASMYJ HMMCV HZBHZ AMCZG VUMBC JCVGJ SZXJJ BVBDD YNVSK VYVHI VGJBA JCNDY ZCJXM BAJCS ZHZDH KJUVY GMCJU VSZYC JXKDS ZIDJB VCSZH NJLCV HEVHI DSZHB AJCDB ZCDOV NZXHZ HIODY JCVHN ZOVUV GVHAV MYGVX IGMCZ VUVHI DHVBD UVIDH IDHZB DHIEG ZKDED IDKVK DSJMI SZXZM GJSZK MEGDN VAJDJ CZBDU ZHZKD AJBVE GJSZX JEGZK DSVGK VMBAJ CCZKJ HMHZA SVXJW JAJUV IDYVH ZBDHI EDEGV NJVYG MOJHM HZIDB ZEGDI JNJAJ.
Since I am a beginner in cryptography, I am not sure which "tools" to use for solving this problem. I made tiny program in Python which counts the frequency of each monogram, each bigram and trigram, but I didn't get enough info for the rest of letters. Any hint that would help me start is more than welcome!
Edit: This question was closed for not having enough information, so maybe this will help.
The most frequent monograms in my text are: $$ ('V', 34), ('J', 33), ('Z', 31), ('D', 29), ('H', 26), ('C', 18), ('M', 16), ... $$ where, in Croatian: $A,I,O,E,N,S,R,J,T,...$ (A is the most frequent, I the second most frequent etc). The most frequent bigrams in given text: $$ ('HZ', 9), ('SZ', 9), ('VH', 8), ('AJ', 8), ('ID', 8), ('JC', 7), ('HI', 7), ('DH', 6), ('UV', 6), ('EG', 6), ('BD', 5), ('ZH', 5), ('KD', 5),... $$ and in Croatian : $ JE, NA, RA,ST,AN,NI,KO,... $ (ordered by frequency, $JE$ being the most frequent one). The most frequent trigrams in text: $$ ('BAJ', 4), ('AJC', 4), ('JHM', 3), ('CVH', 3), ('HZB', 3), ('GJS', 3), ('JSZ', 3), ('SZX', 3), ('JBV', 3), ('VHI', 3), ('SZH', 3), ('JUV', 3),... ,$$ in Croatian:$ IJE, STA, OST,JED,KOJ,OJE,JEN,...$ (IJE being the most frequent,...).