Hi Bruno,
No problem, anytime you are stuck in creating your app, try to always give the proper context, if possible share the .oml file or at least screenshots of the problem at hand. Always select the the application type when you post (mobile,reactive,traditional) as the answers most-likely depend on it. When you have issues with a particular Forge component, you can also select that when you create your post.
As a final suggestion I would like to bring to your attention the free learning site of OutSystems www.outsystems.com/learn
It is the best place to start as a beginner, and will give you a fun step-by-step guidance in becoming an OutSystems developer.
Have fun learning!
Regards,
Daniel