I spend most of my free time working on independent projects, through which I pick up a multitude of skills. Since my projects orbit primarily around Computer Science, that is where I have developed the highest level of expertise.
These skills are measured proportional to each other. I by no means claim to know 100% of Python.
I have spent 8 years learning German and have visited the country multiple times.
These skills are measured proportional to a fluent speaker.