Hi!
I’m having a problem with the mirror modiefier 
Hopefully this picture explains it to you cause I don’t speak english so well :o
Here is he .blend file [ATTACH]386437[/ATTACH]
What is the problem ? (blend file link not valid)
Do you mean it’s mirrored across the global X axis but you have set Z axis in the modifier settings ?
If so has the object got some rotation (you have omitted to show us this in the screenshot !) If so apply the rotation with Ctrl+A
Looks like I slved that By my self! Thanks for your time though. I solved it By moving the object around a little and then putting it to Z 0.