The translations for the core Connections plugin is managed on Transifex. If there are errors or omissions make the changes there. Pulling the connections.pot file would mean that you would have to translate to German from scratch. So, the steps you did very likely contains zero German translated strings. If you want a PO file to save as a MO file, you need to pull the PO file from Transifex.
Now, each extension or template is a separate plugin in WordPress which means each has to be translated separately. The extensions and templates, you would pull the POT or if one exists the PO file for a translation and then make your changes and save the MO file using Poedit.
So… the strings you show in your screenshots, those should be coming from the Link extension. You’ll need to option the connections-link.pot file and create a new German translation. If you do, pleas send it to me and I’ll include it so it will be distributed as part of the Link updates.
Hope that helps!