Mexico City has become one of the most popular and exciting travel destinations in the world. It looks like the Mexican government is aware of that and has created a comprehensive website to assist all of the international visitors going there.
I’m moving to MC in a few weeks and I’ll consult the site for things to do, so it’s not just for tourists.
Here’s the link: https://mexicocitytravel.com.mx/
At this time I don’t believe there’s an app. Hopefully, one will be coming soon. There are other apps available in the Google Play store, but I can’t verify their quality.