Just a little help here...

[BlueBlankey]

Is there any way to moddify- or create a new mesh? Not a static mesh... But an actual mesh.
Sorry for bothering everybody if you can't.

[Dark Lord]

to modify static mesh (and ive never tried this) i believe you would first put a static mesh in your map, right click it, and go to convert -> to brush. then add to that brush whatever you are wanting and then right click and go to convert -> static mesh

to make static mesh its simply putting a bunch of brushes together and converting them to static mesh via that same right click menu

[DooFi]

the best method for creating a new SM is to build it in your favourite modeling app and export it to .ASE, a file format which can be imported into UnrealEd. See the sticky in the modeling category for free tools.