You might want to begin by using the right tools for the job at hand. There are no Torx fasteners in any period Mercedes. They are XZN bolts. If you use a Torx bit, it will fit, but promptly strip out the head. First clean the head thoroughly and try the right bit. If that still doesn't work, you can try an extractor, although you may not have enough room. The last desperate solution is to grind off the head and remove the axle, then use a stud extractor or pipe wrench to remove the remaining stud.