Hi Loed,
Sorry but I have to emphasize this:-
"SAP HANA and SAP BW are very different".
If you know SAP HANA only, you will not to be able to apply what you learned in SAP HANA in SAP BW. SAP BW are using whole different architecture.
However, if there's a project about BW on HANA, then SAP HANA knowledge might help to an extend, but you need to know BW to develop BW.