The first stage doesn't include an interview.
You will do some paper pencil tests, some ATP question just basics nothing serious, there will be a math test and a Englisch test (that won't cause you any trouble). Followed by several computer based test to check your Monitoring and Instrument Coordination. Check out
www.hh.dlr.de under Download you might find some training software. Don' t know your german abilitys but the test is in German!!!!!
If you suceed the first round you will be invited to a Sim screening, i think it is currently hold on a B737 sim.
If you suceed here you will be invited to a 2 day assesment center. Group plays, role games and a final interview. After that you will get a direct answer if you have passed or not.
Good Luck