I'm afraid there's no official way to switch the language.
Quote from Paradox staff:
Hi guys,
The German version will remain a German only version to adhere to the German laws and to avoid any potential issues.
Kind regards
Susana Meza
Unofficially, you could try unpacking the English patch (use
innounp, it's a command line app, launch it like this:
innounp -x -d<path for unpacked files> kharkov_patch_v517_en.exe), and taking the localization out of it. I don't have this game and only guessing here, and maybe this wouldn't work on APK43 at all, so make a backup first. In the patch you will need these folders and files:
data/k43t/loc_eng/packed_data/text_loc_upd.flatdata
data/k43t/dev_updates/loc_eng/packed_data
data/k43t/dev_updates/shared/camps/<various campaigns>/local/loc_eng
data/k43t/dev_updates/shared/root/programs.flatdataPut
text_loc_upd.flatdata and the files from
dev_updates/loc_eng/packed_data into your game's
data/k43t/loc_eng/packed_data folder. Campaign's
local/loc_eng folders go into the game's respective
camps folders. And finally, replace the game's
data/k43t/shared/root/programs.flatdata file with
programs.flatdata from the patch.