I would like to start programming for the Universal Windows Platform with an universal app running on Win10 desktops, tablets and phones. I'm new to programming mobile Windows applications, so I have to learn some basics. I have some experience in Java/Android programming and basic skills in C#.
My problem now is that there aren't much tutorials for UWP app development which teach from the beginning how to program such an app. What I find are some tutorials for Windows phone 8 app development. Are the differences too big or would you recommend to go through Windows phone 8 tutorials to get into the app for Windows topic?
UWP tutorials are sparse and hard to find, it's true. The difference isn't "Big" if you're doing a basic app, but once you start getting into any sort of mid-level apps then yes it diverges from the W8/WP8 paradigm.
One thing you can do is use the Windows App Studio, and create a generic app with an RSS feed, youtube videos or whatever, and download that solution and then look through the code that is automatically generated. I found a few good sources too:
Windows Dev center is also a huge help with example code (on GitHub) and the MSDN has examples as well, if you filter through it properly.
Channel 9 has an absolute beginners tutorial series from nothing to a superhero app.
https://channel9.msdn.com/Series/Windows-10-development-for-absolute-beginners
I also found a good youtube series that covers individual topics instead of a real tutorial series for learning to program apps:
https://www.youtube.com/playlist?list=PLaoF-xhnnrRUNVx-JAfEy_kUrGGaKS7HL