ABAP is nothing but an easy language with SQL embedded within.
As you have already got some coding expertise, the easiest means for you to learn ABAP quickly is to go through the subsequent two steps:
1. Get access to any SAP system (Either get it on your own machine or rent a user ID from someone online)
2. On the command line, enter the transaction code: "ABAP_DOCU". This will start a transaction that starts with the most basic tutorial with sample code and goes on to more complex stuff. It has 100s of examples. You can run the code, make changes, experiment, debug etc. You can press F1 for help, the context help is available and all the sample code works!