Contrary written comments here I can assure you that the sharpening problems is possible if you can keep a file and run. Knives are dull, that's normal. You can disassemble the knife in a few steps and then with a smooth file (ie a fine file) nachfeilen a bit. Then the knife is like the first day. A vise is very helpful, it comes at a pinch but somehow without. Prerequisite: Craft skills, but should be clear that anyway.
