I assume you tried changing the Desktop Language like below and creating the extract (I don't think that changes much... just labels mostly so this is probably not what you are after )
I found some resources that may help you. FYI they are not Hana specific.
You may have read these already but just in case ….
Best way to import and apply language translations of values? Aliases? This one had a workaround which was not ideal but maybe useful
The below link is a little old and has some broken links but still has useful information
And lastly this person below is asking for feedback and may be worth pinging
Thanks Monica for your suggestions.. I had tried that (changing the Tableau Locale) with no success
It really seems to be how to set the locale settings from the HANA connection in Tableau.
As an example, in the SAP BW Tableau Connector, there's the Language Setting.
Wish that same functionality would be available on the SAP HANA Tableau Connector.