for the wdf filter of we have a galaxy model with 5 or 6 fact table sharing the same dimensions table. do we have to wdf filter dimension to each fact table? or is there a better set up?

The Workspace Data Filters are applied within the dataset so if you want to filter data in a particular dataset by a WDF, you need to have it mapped for that dataset, no matter how the datasets are connected. User Data Filters on the other hand are applied to all dataset attributes that are in the LDM along the direction of the arrows.