Yes, you can create these branches. The problem preventing you from redistributing your i18n namespace, so to speak, is that you already have a feature/i18n branch.
Each branch is created as a file under .git / refs / heads, so when you created the branch, Git created a .git/refs/heads/feature/i18n file.
Now you are trying to create .git/refs/heads/feature/i18n/spanish , for which Git is trying to create an i18n folder that it cannot, because there is a file with the same name.
To create these sub-branches, you will need to delete or rename the feature/i18n branch.
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