Need help on how to get sorce files...

ok I am new here and I hope I don't break any fourm rules.

I need some help, I have programming experience in c++ and c# and I also know some web programming and some python.

I know what programmers know well at least on a basic/intermediate level.

I want to reverse engineer a program it's a web program.

I been tryring to learn the structure and which language it is.

Well this is what I got so far, I think it's a java app the program can be installed with a tomcat apache server meant for java apps.

how would you go on learning the structure?? do I need the source code??

Try pming Jetamay i believe he knows