AFAIK, the earliest "German" trading establishment in the 19th century was founded by the Hamburg-based merchant Carl Woermann in 1854 in Liberias capital Monrovia. In 1862, a second establishment in Libreville in French Gabon followed. In 1868, a third trading post, this time on a hulk in the estuarry of the Cameroon River.
If, for some obcure reason, the Mayors and Senate of Hamburg had seen fit to declare the protectorate over the lands on the Biafra Bay, everyone would have laughed themselves to death. But the keeping up the claim, the German Empire inheriting it in 1870, and then ...
Nah. In 1868, Hamburg was already part of the North German Federation , with the Prussian King as the one who would decide those things. And Bismarck who would, de facto, day no.
Forget it.