The Mormon Church has many of the Luxembourg civil records online.They are not indexed but you can browse them.For the marriage record of Johann Birnbaum and Margaretha Hansen, go to famlysearch.org.
Do not put the names in but scroll down and select "Continental Europe".On the left hand side, find Luxembourg and select.Then select "Luxembourg Civil Registration 1793-1923.It has a little camera icon next to it which means there are images.Go down to view images and select "Browse 494, 792 images.Scroll down to find the community that you wish to search.In this case, Niederanven.Click on it.Select Mariages 1814 (acte 12)-1890 -- Décès 1796-1849
There will be a box with the word image next to and a number in the box.Put in the number 329 in the box and hit enter-do not use the arrows.This will bring the marriage on the left side of the ledger.
If you want to know more about the records that the Mormon church microfilm, see Therese Becker's website:
I don't think it has been updated since the images were made available online but it will tell you about the records.Not all Luxembourg records are online but you can order microfilms at your local Mormon (LDS) Family History Center.You should be able to find where they are using the main website.
You can save the images to your computer and print them out.One one for the marriage is really nice and clear.