Reviving this zombie thread as I have to translate the same quote.
Except it's not the same: it's "Das schönste Denkmal, was ein Mensch bekommen kann, steht im Herzen der Mitmenschen".
As a reminder, the one in #0 is Das kostbarste Vermächtnis eines Menschen ist die Spur, die seine Liebe in unseren Herzen zurückgelassen hat.
I've also looked up Albert Schweitzer quotes and found "The only thing of importance, when we depart, will be the traces of love we have left behind" on English sites.
However, on German sites I also find "Das einzig Wichtige im Leben sind die Spuren von Liebe, die wir hinterlassen, wenn wir weggehen".
None of these have any sources at all, so who knows what game of multilingual Chinese whispers might have taken place to produce any of these "quotes". They might all be the same thing translated back and forth. They might be two different things.
I don't suppose anyone has any clue what the original is/originals are or where they might come from?
I also see the one in #0 attributed to both Vinzenz Erath and Irmgard Erath (two unrelated people).