This question is not off-topic. In past I also use notepad++ for programing. Today i use Atom. You can find a lot questions about notepad++ in stack overflow - for instance: Removing duplicate rows in Notepad++ or this Convert tabs to spaces in Notepad++ (and many more). So please do not give minus points to this question.
Answer: I assume that when you go to menu>Encoding you will see 'Encde in UTF-8.'
I use this site to create part of my answer: https://superuser.com/questions/576431/notepad-inserting-special-unicode-characters-in-utf-8
If you see character codes like \u0119,\u015b\u0107 in your file this probably mean that they are just on encoded - and their codes are put expliicty as raw text.
So to change this codes into UTF-8 characters, go to
- menu>run>run> type: charmap> click run
- the windows charmap will show up, so check ''advanced view' an there put you character code (without \u prefix - so for instance only 0119) in filed 'go to Unicode'. Then click on 'select' and 'copy' and close window
- Then go to menu>search>replace and in filed 'replece with' past you character, and inf filed 'find what' put its code (with prefix, for instance \u0119). And click 'Replace All'
- Do steps 1-3 for each character code (you can check thad your done when you click menu>find> and type '\u' in "find what". If you not find any code then you job is end.