@RinHara5aki
Thank you very much for your advice, your optional Combo and your finishing tips =], but I figured out, why I missed that often a few minutes ago and in the end, it didn't have anything to do with Jin ^^
In fact, I just didn't input the "a" fast and soon enough. The outcome was, that the opponet flew to high after the drive before I hit him with "a" which then pushed him too high for the following "j.c". It took me hours of frustrated moments to figure that out...
Sometimes it's so hard to find the mistakes in the timing ^^ (or maybe that's just because this is the first fighter I really want to learn xD)