How to read file/write to a file in UWP C++

So does anyone know how to write/read files in UWP C++? "Normal" file streams that worked for me before in console apps like fstream doesn't work, I've been googling that for hours and I learned that UWP has no access for anything. I found this: https://docs.microsoft.com/en-us/windows/uwp/files/quickstart-reading-and-writing-files but it's C# and everything else in the internet is C# aswell.. can't copy with that, I got stuck.

My program is a simple password manager, what I want to do is implement 2 functions:

1. read 3 TextBoxes, get stuff from it and put it one line then add the line to a file
2. read whole file full of passwords and put it in a TextBlock

Help please