You can install Azure Devops Server in various languages, however, as of now, you can not have different languages enabled in the same Azure Devops Server.
Refer:
https://learn.microsoft.com/en-us/azure/devops/server/requirements?view=azure-devops-2022#languages
See the below thread that explain an issue similar to what you are facing.
https://developercommunity.visualstudio.com/t/azure-devops-language-overide-for-projects/716831
Hope this helps