This came as a result of the meeting between the German foreign minister, Dr Steinmetz, and President Muhammad Buhari.

“The militants engage in sophisticated sabotage, using skills
they had gained from trainings either by government, or the
oil companies, to vandalize installations deep in the sea. We
need to understand who the real agitators are, and engage
with them, so that confidence can be restored in the region,”
the President added.
President Buhari said the Niger Delta situation was more
complex, since the militants had no central command, and
some of them were mere extortioners, but promised that a
handle would be found to the unrest soon.
Dr Steinmeier, in his response, said Germany was happy to
hear of the strides taken by the Buhari administration against
insurgents in the North-east, adding that they were equally
willing to lend a helping hand in resolving the crisis in the
Niger Delta.
Applauding the war against corruption, Dr. Steinmeier said it
had his country’s support, adding that Germany was also
interested in investing in renewable energy, gas exploration,
mining, among others, to boost Nigeria’s economy.
“Germany will support development in Nigeria. We want
closer cooperation on migration issues, urbanization, and
supporting the navy with equipment, training and
intelligence , “the Foreign Minister said.

http://www.vanguardngr.com/2016/10/niger-delta-militants-objective-is-to-colonize-nigeria-economically-buhari/

I also wonder why Buhari can't allow our own foreign minister to meet with the German foreign minister as is done elsewhere.

Who are you to say that?

They are most welcome. I'm ready to offer some help