For content in editable region, you will need to translate the content for each language.
For text in templates, you can use the localization resource strings. For example: instead of hardcode "Welcome" in the template, you can go to Localization app, create a resource string for "Welcome", then in your template use ASCX or macro to load the string
https://docs.kentico.com/k11/multilingual-websites/setting-up-a-multilingual-user-interface/working-with-resource-strings