since you only provided this one sample, its diffucult to test edge cases and fine tune the regex, but the following should give you a good starting point:
((?<=LUKA\sRIJEKA\s)\d\d\.\d\d\.\d\d\d\d)|((?<=\sLUKA\sRIJEKA\s\d\d\.\d\d\.\d\d\d\d\s\d\d:\d\d:\d\d\s)22[^\s]+?MRN)
i have split your problem into two match groups, one that looks for the date and one which looks for the MRN.
i would advice you to read through this article: Regex lookahead, lookbehind and atomic groups. since the solution heavily relies on lookaheads. for creating and testing regexes i would recommend you to use one of the many websites which come up when you search for "regex online"