I’m trying to study and understand how to use aber und sondern (as “Konnektoren”). In my language (Italian) there is no difference in translation; both mean something like but.
I can say for example:
Ich muss in die Schule gehen, aber ich bin ein bisschen krank.
Ich spiele nicht Tennis, sondern ich spiele Fußball.
In these two examples (taken from my book), I don’t see any difference. Could I also use sondern in the first sentence and aber in the second one? Would that make a difference?