Hey Ali,
first you should ask them to send you the specs of their aircraft. Without that you will get cought in the technical interview.
You should know how a engine functions, what you are looking for when making your pre departure checks, you will have a number of ATPL questions. Mainly meterology and some tech. And they did not make it easy on me.
But as I hear it was not easy for everyone...:-(
you have some test as well... for like basic character issues which is quite long. they monitor you during that. As last thing you have to talk within a group, on special topics. I had 6 topics in my group...i think, airlines and labor, reputation of african aviation, safety measures, passengers and low fares, recruitment, ....hmm...do not remember the last one. But that is about it. Ah yes, and at the start you get to go to the validation exam...basically there is nothing you will not know due to your lessons you get in advance.
good luck