Thank you cr1776. This makes it clear to me.

If I want to compile 0.14.2, lets say in some weeks, is it possible to just run the usual
./autogen.sh
./configure
make
sudo make install
or do I have to delete 0.14.1 before this procedure on my Linux System? So my question is how to "upgrade" the Core Client to a newer version.
I installed the Core only on fresh systems so far.
You don't have to uninstall or remove any of the previous files. Make install will overwrite the old ones with the new ones automatically.