Thank you for bringing this to our attention. We have been looking into this and found a technical issue on our site, which we are currently working on fixing.
While we fix it, you can access the talks and lectures page by making sure you are viewing the page in the language you registered in. In your case you registered in Spanish, so the link you should follow is https://arkitekturo.com/es/competition/bauhaus-campus-2021/talks-lectures/. (notice the /es/ part).
You did nothing wrong, the site should be able to tell that you are a registered user, regardless of which language you registered in, and we are currently looking for a solution so that it does just that, but until then the link above should work for you. Please let us know if it doesn’t.