Are there available somewhere numbers of how much time is needed to learn programming languages?
I do understand that this does, very much, depend on the person/learning-method. But I'm more interested in seeing some dynamics among languages, which I guess would be less 'personalised' - i.e. I would like to see division between HARD & EASY languages
Well generally speaking, a language is only as hard as the libraries it has. Take the Windows API for C. It's hard and at many times inefficient for making programs to do simple things. That's where .NET framework comes in. You can still use C++ with the .NET framework. The language isn't any easier, but the libraries you are using are easier to work with.
Learning Java takes quite a while, especially for a beginner. However after my first 5 minutes in java I understood the Swing library and could make a simple program. If I wanted to do the same with the Windows API it would take me a good month.
In the end, mastering and understanding the innards of languages is time consuming, but is directly proportional to the effort spent.
C++ can be learned in 21 Days (as the book goes) but it takes years to fully understand it.