I can use application control API to open s-health app, but how I can go directly to the sections of s-health like heart rate or step count ? watch faces created from galaxy studio can do this so it should be possible.
Samsung Health is a proprietary algorithm and is not public.
Galaxy Watch Studio tool has limited access to Samsung Health API the designers do not have direct access. Tizen developers do not have that access. You would need to be a Samsung Health partner to get that information and I think it is only available on Android for partners.
What Tizen developers can do is access the sensors and create their own algorithm for the functions. It will probably never be the exact same as Samsung Health reports.
Samsung Developer Program