I made a fresh install of darktable for the first time. My Windows OS display language is set to English but darktable defaulted to a German UI presumably because my location is in Germany and the location set in the OS is also set to Germany.
Where did you download darktable from?
The language can be selected if you click on the Global Preferences icon (the cog wheel to the right in the top bar) and click the General tab to the left.
(You will have to close the dialogbox and restart darktable for it to take effect.).