Hi Manuel,
Thank you for reaching out to Microsoft’s Community.
We understand that you have issues logging in to Microsoft Learn.
We would like to confirm that we have limited access to the Microsoft Learn Platform and we can only guide you to connect with their support line, which can only be reached through the Feedback forms in the bottom part of the Microsoft Learn support - Troubleshooting known issues | Microsoft Docs
What we could suggest, is to perform basic troubleshooting steps to rule out system related issues.
1. Use InPrivate browsing in Microsoft Edge.
2. Clear browsing history, cookies and cached data.
3. Sign in to the Microsoft Learn Platform.
If it does not work, please fill out a form and attach the error message (see image below).

Please let us know the outcome.
If no response is received, we will close and lock the case in the next business day.
Daniela Duran.
Microsoft Certified Professional Services Center.
Support: Monday – Friday