Hi
1.
the place you are looking for could be Hamburg Altona.
A while ago, whilst looking for a John Macdonel, i found out that there was a British community in Hamburg at the beginning of the 19 century.
I found some info on John Macdonel in the state archive in Hamburg.
https://recherche.staatsarchiv.hamburg.de/ScopeQuery5.2/detail.aspx?ID=1972225An online search for Macdougal (Mcdougal) brought no results.
2.
Hamburg was incorporated into the French Empire on February 13, 1811.
Therafter all records were administrated by the administrative office (Maire) of the French municipal council. The Hamburg State Archive has records of the children born in this period.
Register "Kinder im Register der Mairie 1811 - 1815"
https://recherche.staatsarchiv.hamburg.de/ScopeQuery5.2/detail.aspx?ID=1069832To search these files you would have to visit the archive in Hamburg and search the records personnaly.
3.
Members and subscribers of the „Geneaology Community Hamburg“
https://vereine.genealogy.net/GGHH/have access to these records.
One of their members kindly did a search on MacDougal and found a marriage record that could be a lead.
Plate, Johann, * abt. 1806, married. 05.03. 1837 HH-Petri Hamburg, Holzdamm
occupation servant, born in Hünkenbüttel / Stade, religion catholic
Macdougal, Hendrina Maria Cornelia Gertrude, * abt.1803, married 05.03. 1837 HH-Petri
born in Emmerich / Preußen, resident in Hamburg, Voglerswall; Spinster
Parents: Joannes Macdougal and Anna Catharina Richée Child:Johanne Malwine Gertrudis Franziska * abt. 1837
married 11.04. 1865 HH-Petri with Evers
4.
By the way. You mentioned Ernst Kohfahl as a witness. A search for Kohfahl gave several hits
5.
This is all speculation. It´s a long shot, but could be of relevance.
What it does prove, is that there were Macdougal´s and Kohfahl´s living in Hamburg at the beginning of the 19 Century.
Dave