samsung galaxy s3 will not boot up (soft brick)

hey

my samsung galaxy s3 GT-i9300 will not boot up ,only shows the samsung logo
after trying to ROOT my device the problem came in
i tried flashing stock md5 using odin nothing works :(
and after trying to flash the md5 my samsung has gone even worse it now says " FIRMWARE UPGRADE ENCOUNTERED AN ISSUE PLEASE SELECT RECOVERY MODEIN KIES AND TRY AGAIN

pressing up - power - and home will not work the only thing that works is download mode

HELP ME PLEASE