I got back from a long trip. The avocado tree survived, but its a bit struggling. It probably didn't like the 15 °C that was in the house until I was away... Now Im back and the temperature is back above 20 °C, so there should be some improvement in the next weeks, although I don't expect much growth until summer is back when I can put the small tree outside again.
A random avocado grow
One day we went on one of these big shopping trips to buy groceries. We also picked up an avocado that we ate. Then we pierced the seed with three toothpicks. A month or two later a little root started to appear. Now its on its journey to become an awesome tree ;)