Are you referring to the agenda community and tutorials, or to the Agenda app itself when it comes to picking the language? The app picks up the localisation from the language setting of your Mac and/or iPhone and iPad. The community is indeed a different story, it’s hard to provide all materials in all supported languages, and keeping them subsequently up-to-date would be even harder. If you have a specific question, one option is to ask for help in the specific page for your language in the Languages section of the community, in your case this one: Spanish - Español
The translators are Agenda users as well and I’m sure that they’d be happy to help you in your native language if you post your questions to them.