A couple of suggestions-

On the quay by... (doesn't one say 'on' the quay?)
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His heart was full of woe.
(Dann, not dahn- it means then or next)

On the shore a maiden stood weeping
Waving farewell for long after. Afterwards?

Fare thee well, my sailor, adieu!

Idiomatic translation into something singable is very difficult; this is why most songs rendered into English end up departing in meaning from the original.
I have translated a bit of botanical and geological German into English, including a book, but scientific German is a 'whole nother language' from that spoken by the average German.
In other words, my efforts on a poem or song ain't worth much.