Use the health sync app in PlayStore.
https://play.google.com/store/apps/details?id=nl.appyhapps.healthsync
You can only choose one direction for sync. Either add samsung data to google fit or the other way around.
I used this same vendor for my Gear S3 metal band. No complaints at all for the band they offer for the Gear S3 and the Galaxy Watch4 Classic.
Just ordered today LDFAS Compatible for Samsung Galaxy Watch 4 Classic 42mm 46mm Bands, No Gaps 20mm Stainless Steel Metal Watch Strap Compatible for Samsung Galaxy Watch 4 40mm/44mm Band, Black https://www.amazon.com/dp/B09GG58XPX/ref=cm_sw_r_apan_glt_fabc_PCDWE80PJKJNCPZMQWHD?_encoding=UTF8&psc=1