Dear Allaa waked.
I'd like to answer as my experience.
1. CPM only can read project object that already made from ECC PS.
You can assign 'CPM master Project' with 'ECC PS project'.
2. Some data can read automatically to CPM when you change data from PS such as WBS or activities. but when you change some data in CPM, you should make BAdI implementations or configure 'Transfer to ECC' IMG to sync with ECC PS. It depedns on data that you wants.
Best Regards.
Kwangkyun Choi.