[Q] [Need Help] i9500 without download mode, but android system recovery 3e topic

hello,

i got a i9500 with chinese firmware installed:
baseband: maui.11amd.w12.22.sp.v17
kernel: 3.0.13
build-number: jdq39.i9500zhuamde

my problem is, that its not going into download mode so i cant flash anything with odin, because its not recognised.
when i press vol down+home+power i get into "android system recovery 3e" which gives me at each .zip "signature verification failed" , i cant toggle it anywhere.
if i press vol up+home+power i get into a system testing tool, without helpful function.

towelroot didnt do it and zips to root the phone arent flashable.

do you have any ideas. i spent two days for finding a solution. but no chance.