I downloaded Outsystems and I have a question for training.
There is a "path" to do a correct self-training? I find some videos, the offline help, but I have some difficult to start with a "learning program" to have a good software knowledge.
Another question about "Silk UI", I find on Youtube a video (SILKUI from basics to advanced). To develop a web application for desktop and tablet, it's better to use the classic Outsystems environment or to use Silk UI? 
Many thanks for the help.
I would suggest that you take the online class found here - http://www.outsystems.com/learn/instructor-assisted-training/online-class/

As for using Silk UI, that's definitely where the platform is headed so I would use that though I'm not sure the online class uses it.

Hope this helps,
Thankyou Curt.
I just finish the registration...
Hello Francesco,

Silk UI Framework also uses the classic Outsystems Environment as a base.

The major advantage of Silk is that it helps you build complex User Interfaces, just by draging and dropping elements to your page. So basically, Silk can help you accelerate your front end development, by giving you common patterns and structures ready to use, without having to code CSS or Javascript.

Besides the Silk UI from basics to advanced youtube video,  you can also find more information on the Silk UI website.

Please let us know if you have any questions.

Samuel Jesus