Why can't I delete emojis downloaded from Huawei Themes Manager app?

[Android Central Question]

I didn't really like the stock emojis on my Huawei P9 lite phone so I downloaded some new emojis from the Huawei Themes Manager app. Now they have become permanent on my keyboard and I can't seem to get rid of them. Even the emojis from Facebook Messenger have been changed. Uninstalling and reinstalling seems to reset the emojis for a few minutes but they still change back again, even after I have uninstalled Huawei Themes Manager. Any ideas how to fix this?