nephele: Me 2 days ago: 
> "Then let's put my firewall skills to the test ..."
Now I have to say that I failed ...
But on the other hand I now know this for sure: 
> "I think you have to reload ufw to activate changes but I'm not 100% sure."
Luckily it only took me around 3 minutes to figure out that I forgot to reload the firewall.