There are many funding opportunities for international cooperations and for the internationalization of research.
On the website for the BMBF International Cooperation (Kooperation International des BMBF) you can take the first steps to finding opportunities for world-wide collaborations. You can also do research to decide if you would like to start networking or even start a specific project.
Over the BMBF International Office you can search for region-specific funding opportunities for international collaboration preparatory measures.
You can also find country-specific funding programs through the DFG.