Bewährt — proven, tried and tested. It is praise. The usual pairs are bewährte Methode, bewährte Praxis, bewährte Technik, a proven method, practice or technique.
Altbewährt — proven for a long time.
Neumodisch — newfangled. The word for something new that has not yet earned its place.
Never change a running system — said in English, in German offices and IT departments.
Was der Bauer nicht kennt, frisst er nicht — what the farmer does not know, he will not eat.
Prüft aber alles und das Gute behaltet — but test everything and keep the good. It comes from Luther’s translation of Paul’s First Letter to the Thessalonians.
Das haben wir schon immer so gemacht — we have always done it this way. Germans quote this mostly to mock it, as the typical objection to anything new.
Probieren geht über Studieren — trying beats studying. It is the proverb on the other side.