Maybe it is just the German translation... but the help text above the left file box is confusion and points to a non-existent button. It says one should use the "import files" ("Dateien importieren") button to add media to the project - but there is no such button visible. 

There is a button in the toolbar that is named "Mediendaten zu Ihrem Project hinzufügen" ("add media data to your project"). Maybe this is meant to be the mentioned button but shouldn't the shown instruction then name it correctly?

There also is a button called "import files" in the context menu of the file box - but as pitivi aims to be very easy with high usability the help only should refer to visible buttons - or say where to find that button in case it is not visible?

I had two people independent from each other who did not know how to start with pitivi because they relied on the instruction and were looking for the mentioned button near the box and could not find it.   

Maybe it would have been easier for them if the instruction would not have mentioned that button at all because then they would have presumably clicked on the button in the toolbar.

It is a minor gui (or translation) bug for me - but stopped some others from working.