After someone recommended to use the daily elementaryOS build on reddit to e.g. update the system, I went ahead with:
sudo add-apt-repository ppa:elementary-os/daily sudo apt-get update
and went for the upgrade afterwards. However the whole procedure left me with an OS without the Terminal which also can't be installed via AppCenter (gives me the "installation post script error 2" error message).
What options do I have? Do I have to go for a wipe?