1. the user generated content will be a little challenge but not impossible if you really need to as there is AI.
  2. emails. in my app I use postmark. I have an “only when: users’ preferred language is en_us” and another action with the same only when but for another language.
  3. The dropdown issue is quite easily solved with option sets. Try searching this forum for multi-language. Erlendne has a good solution for example.