It doesn't really matter much to me whether the projects somebody has worked on are open-source. But if they can't be demonstrated to exist, that's something else entirely.
For what it's worth, some Googling turned up these links:
https://github.com/mochja/odovzdaj.to
but it shouldn't have been so difficult to find them.
I would question you on the specific things YOU wrote and how YOU would solve problems.