Regarding the content generated by the AI, You can put your AI settings in English and set your preferred language to the one you prefer.

Once you set your AI settings, all content generated by the AI will be generated for you in your preferred language and you will be able to modify it and publish posts in that language as well.
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You can find the AI settings by heading over to General tab (https://app.taplio.com/settings) in the Account Settings and scrolling down to the AI settings section.
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It's important to note that, at this moment, there is no option to fully translate Taplio to other languages except for English.