I have not worked on MDG but in our last project we extracted the data from SAP MDM Repository. MDM Repository data is stored in the form of tables and views in Database. As per SAP MDM User guide only Oracle, DB2 and SQL Server databases are supported by MDM. You need to check the MDG user guide.
Once you have the database which contains the repository data then you can simply create a Datastore of Database Type and connect to MDG Tables(Source) and then load the data in SAP HANA S4. Data is stored in the form of Tuples in MDM repository so the View name in Oracle wil start with TU_xx
I hope this is clear
Refer to SAP Support Portal for more reference
SAP Master Data Governance 7.0 – SAP Help Portal Page
Regards
Arun Sasi