Hello,
If you are looking to get into Project Management as a discipline one of the industry certifications like PMP from PMI or Prince 2 is good foundation. You already have this so you are good to go to domain specific certification.
If your goal is to work in the SAP project delivery space then understanding the SAP implementation methodology and tools is important. The C_PM_71 certification exam from SAP and associated curriculum will provide you with that.
Good luck.
Jan