If using PR, do not use "duplicate." This is a known issue. I have found that, while you can get the changes to appear in the monitor, the 2 streams are not independent - changes in the duplicate may show up in the original.
After you make stream one (e.g. English), export as srt (ensure the name is different than any other imports), then reimport. Any thing other than basic styling will not come through correctly, so if you have important styling/positioning, this requires more planning.
Consider creating the multiple streams with a third party program, for example, SubtitleEdit, which will do translations.
If this does not make sense, let us know, and we'll provide more specifics.