Vlacko, in Cyrillic this text is more understandable. I could guess that Кунем ти се Богом (it sounds almost like клянусь/клянёмся богом) could be i/we swear to God, and чин in this context means act (such as почин in russian) чуять - to hear in ukrainian( to feel in russian) and I would never confuse ста/шта and so on.
BTW бранить in modern russian means to abuse, although we still use поле брани as battlefield so i thought бранити means to fight.