As many of you know we released a new update today to introduce some really cool new tools in Fusion 360.
In the software world sometimes things sneak through the cracks and require additional updates. We introduced the ability to change the default language in the update today although it is still in its early stages and not intended to be in this version of Fusion 360. I would recommend that you don't change the language from English at the moment. We are going to push out an update tomorrow that will remove this ability for now and we will re-introduce it in a coming update likely early summer.
We hope you are enjoying the new update and sorry for the inconvenience.