Support: Contacting Duolingo
How long will it take for the Duo team to answer your questions ?
Depends on the question :)
Honestly, the support email is notoriously slow/unresponsive. You're usually better off posting your issue in the forums and seeking help from other users that way. I've had some luck with quick responses from the email@example.com address, but obviously that line is intended to solve issues with people causing a ruckus on the site, rather than just general support issues.
You will get an automated acknowledgement with a ticket number very quickly but you may never get an answer to your question. If you have reported a genuine bug then you may get a response when it is fixed but with +50 M users and less than 30 technical staff, I suspect they have to be selective in what reports they respond to.