You can't change this on the fly, but you can change this as often as you like. There's two ways to get to this menu
- Open Internet Options from the Control Panel or from Internet Explorer (Tools > Internet Options).
- In the General Tab, click the Languages button at the bottom.
- Click Set Language preferences.
- Go to Settings in Windows 10.
- Click Time & Language.
- Click the Language side menu option.
Then, click Add a language, or if you've already added a language, you can re-order the list of languages you have chosen so that your preferred language is on top.
From here you can add whichever language you want. The reason I say you can't do this on the fly is that Microsoft Edge will need to be restarted before it will detect your changes.
To disable spellcheck, go to Settings, type "spell check" (without quotes) in the search bar and hit Enter, and then you will see the option to disable highlighting or autocorrecting of misspelled words. Again, Microsoft Edge will need to be restarted before it will detect your changes, if you have it open when you make these changes.