Oh, I didn't notice that Joerg typed in "na coillte clómhar" instead of "na coillte cnómhar", "cnó" being a word for nut. Brían had spelled it correctly.

There are loads of hazel trees in Ireland. They used to be popular for coppicing. The "scolb", a hook for holding a bundle of thatch down on the roof, is still often made from hazel. Not that the country is still full of thatched houses, but there are some. Joerg probably has an incorrect image of big, glossy hazelnuts; the uncultivated ones are smaller. Though a romanticised image would fit the song okay

No, I'm not keen to do translations. Did you not notice that I left this one to Brían? Between his work and the verse from the Dubliners, readers have a good enough idea of the gist of the poem. I saw a few messages about 'Sé Fath mo Bhuartha on one of the Gaelic-L discussion groups(Gaeilge-A, etc) and there was only one response to a query about "mil ar luachair" that the word "mil", honey, is used figuratively to describe the dew drops glistening on the rushes.

I'm not clear whether Joerg intends to compose a SINGABLE translation into German. Of course, often in translation it is more important to convey the sense of the words rather than to translate them literally.
I think an easy way to illustrate this principle is to think about idioms. In some languages it rains "frogs", but I should translate that into English as "cats and dogs". The English "swimming against the stream" becomes "ag snámh in aghaidh an easa", "swimming against the waterfall" in Irish. If I was translating from the Irish, I might want to convert the expression to the usual English one. At other times I might choose to be more literal in order to emphasize the exotic nature of the material, or in this case because the Irish expression sounds stronger.