1-What is the difference between pocket code and pocket paint?
Pocket Code is a visual coding IDE and interpreter for Android for the Catrobat programming language. 
Pocket Paint is associated to Pocket Code. It is a graphical paint editor application for the Android platform that, among others, allows setting parts of pictures to transparent. 
2-For working in pocket code or pocket paint Which code have I download catroid or paintroid?
The android-development-project-name for the publicly known application pocket code is "catroid" the iOS-development-project-name is "catty". Both "catroid" and "catty" are known as Pocket Code; however, first one is developed for Android the latter for iOS
3-What is Ticket training?
In order to structure development, we have tickets that are used by developers to get information on what needs to be done. Moreover, we have an agile development workflow that includes eXtreme Programming and Scrum. As one needs to know how the workflow is applied and be used in a proper way, we decided to have an introduction ticket that guides a new user through the workflow and provides a chance to get familiar with our environment. This "introduction ticket" is referred to as "training ticket" as it provides training on how to use our ticket system.
4- what have i to do from now until 19 April neither Proposal?
Please see the official timeline and prepare, following our guidelines, and hand in your proposal -before- the deadline. 
5-Is there issues in github is recommended in github to dive deeper in code and be accepted?
It depends on the project you are aiming at. For Pocket Code on Andoid the best would be to have a look into the source code of catroid, if your project is related to Pocket Paint on Andoid you might want to look up the source code of paintroid. Please be aware that this will not guarantee that in the end you will be accepted.
6-what is JIRA?
JIRA is a proprietary issue tracking product developed by Atlassian that allows bug tracking and agile project management. 
Also which one is the app we will work on?
It depends on the project you are aiming at. For Pocket Code on Android it is catroid, if your project is related to Pocket Paint on Android it is paintroid, or develop games in Pocket Code itself.
See you around,
- Catrobat Org Admin