When doing a clean install of Windows 10 all the apps in Windows was using Swedish. Apparently Microsoft thinks that if you use a Swedish keyboard you also want the apps to run in Swedish, even if you selected that you wanted to run Windows in English.
The primary language in Windows 10 seems to be selected from which keyboard you are using.
To change your primary language, follow these steps:
Swipe in from the right edge of the screen, tap Settings, and then tap Change PC settings.
(If you’re using a mouse, point to the lower-right corner of the screen, move the mouse pointer up, click Settings, and then click Change PC settings.)
Tap or click Time and language, and then tap or click Region and language.
Tap or click the language that you want to use, and then tap or click Set as primary. The language you choose will appear at the top of the Languages list.