Welcome to the community @Nabil!
Thank you for your interest in DHIS2. Would you please explain more about the use case? Are you working on a DHIS2 implementation? Please have a look at play.dhis2.org instances, you can have a look at the Data Visualizer app after logging in.
For learning more about dhis2 please read the post below by @Matthieu:
The DHIS2 Online Academy is introducing new courses on our updated training platform!