Hello Juan
Storing the CheckBoxes the way you are attempting is not a good way to store information.
Have you made use of these resources to help you learn to use the AI2 tools. A very good way to learn App Inventor is to read the free Inventor's Manual here in the AI2 free online eBook http://www.appinventor.org/book2 ... the links are at the bottom of the Web page. The book 'teaches' users how to program with AI2 blocks.
There is a free programming course here http://www.appinventor.org/content/CourseInABox/Intro and the aia files for the projects in the book are here: http://www.appinventor.org/bookFiles
How to do a lot of basic things with App Inventor are described here: http://www.appinventor.org/content/howDoYou/eventHandling .
Also look here App inventor español. Offline. Tutorial. Ejemplos. Instalación. Códigos. Juegos. Curso gratis de App inventor. and here Tutorial Index | imagnity for more tutorials.
Learn about components Component Reference
and visit the Library The MIT App Inventor Library: Documentation & Support Help>Library on the MENU
A similar app to what you are attempting that can save data is discussed here> Working with Lists and TinyDB It may give you some ideas about how to structure your app.
Here is another example Fruit Stand - Google Docs
If you post the aia of your Project, someone might help you try to fix your Project; however I recommend you store your data differently.
Regards,
Steve