Converting python to C# is an option. Are there any ready-made converters to do this? Or are there any other ways to realize a uwp app from a python code? You help is very much appreciated.
I think your best bet would be converting, and then learning a little. Based on the difficulty and how many different or new things you need to learn to alter the app, you should maybe just consider learning the language basics and then go from their creating it in C#, You'll gain some skills in another language. Who knows maybe like it more. 
You could try one of many other converters, to another language that works or even convert to a language to convert. There is a C++ converter of some kind that may be a bit better, and then I guess perhaps you could convert from their with other tools, seriously may work better. More things are out their for C++ than C# and considering the commonalities, I bet a decent converter exists. Maybe convert to C or C++ or even Javascript because they have good conversion tools. With Java Script it would be kind easy to convert and learn a tiny bit to fix if you have a converter to C#.
Otherwise converter between the two Python and C# isn't a main priority for many people, if anyone at all. Since they are so similar yet the Syantax is so different, it must be hard to create, and usually people stick with one or the other, or learn both because they do a lot of Object Oriented Code. I mean just Syntax needs to be learned. Also the modules mentioned or packages probably wont ever convet to C#. I'm pretty sure they would just need to build the packages from the ground up for C#, witch is possible.
How to use python code to create a universal windows platform application?