for a bachelor it's not really defending. you just have to tell them what you have done and what you got out of it, cuz' it's not like a master thesis there you really have to come up with the entire idea of the project. for a bachelor it's just: we want to know this, we can do it this way, do you want to do this project, kinda like that. they ask some question to see if you understand the project (after the presentation), but no real defense.
and I already did that ^^