Irrlicht Engine

using the load irr tutorials we have created our own irr maps, now we created a basic ai where when you are a certain distance from the enemy it chases you in a fly straight animator, however this is very stupid and a slight dodge and they run past you, but they also ghost through the walls of the map, is there a way to fix this or do i need a new approach which the enemy movement rather than a fly straight?

For such things I'd generally suggest to integrate a physics engine to your project. You might need it anyway at some point (shooting guns and the like). You find quite some wrappers for common engines (Bullet, Newton,...) here on the forums.
Regarding the steering of your AI you might wanna go though the pathfinding literature. There are lots of articles as well as code examples around.