Hi,
Start with module builder, its in the Suite admin panel. From there you can build and deploy basic modules with relationships to other modules. Once you have your basic modules set-up this will give you your database tables and a starting platform to begin coding the rest of your functionality. Suitecrm is very complicated and you cant just go in and start adding tables to the database and expect it to work unless you really know what your doing.
Good luck
Thanks a lot! Sorry for stupid queston, but which programming languages should i know to developt it? Php, javascipt?
PHP and JavaScript will be needed but TBH if you have to ask this then I think you would be better off picking something else for your course work. SuiteCRM development is not easy for total beginners, your setting yourself up for a lot of hard work. 
Thanks a lot for your advice! But i don’t want to give up 
At least i should try to do something.