So I found out exactly how to do this. It took me a few minutes to figure out what tncool was saying but do this:
Settings
Lock screen and security
Other security settings
Device administrators
And in Device administrators you need to unselect Outlook. Once you've done this you can remove...
Press the cog icon on the keyboard then under Input languages select "Add input languages". From there you should be able to add whatever you wish!
From now on you can swipe on the keyboard's "space bar" and select your other langauges