Is my first time when I try to build rpm.
I start with Krita source code to test this feature.
I don't know all tools involved into build rpm actions and all outputs errors ...
Most people who build rpms have prior experience experience compiling and linking programs, building libraries, etc. Learning generally goes better if you start with simpler tasks and build up to your objective. The best programmers I know are very skillful at breaking complex projects into relatively small simple steps.
Maybe my file krita.spec is wrong.
Why the Fedora team don't have good tutorials and examples about how to build rpm files?
Adding to Todd's very helpful post: unless you get a spec from a current Fedora package there is a good chance it will need some simple tweaks.
There are many distributions that use rpm packages, so you can also look for tutorials and examples outside the Fedora documentation. Furthermore, the demand for Linux developers greatly exceeds the supply, so the people who are skillful at building rpms have more work than they can handle.