@gsarvadnya I really appreciate your reply.
You can find below the steps produced the bookmarks duplicates issue:
I installed brave on desktop and Android then imported bookmarks from Chrome on desktop then I synced bookmarks for the first time from desktop to Android. Bookmarks synced successfully. Then I added new pages to bookmarks on desktop then I do sync again, I found old bookmarks duplicated with the new ones on Android.
For the bug you mentioned, I see this one and mine are the same as this one also happened with me. We can conclude that bookmarks duplicates occur when resyncing from desktop to Android and vice versa.
For passwords sync, I hope it will be implemented soon.
Thanks a lot for your help.