help, twrp : no system and shows internal and external storages 0mb

hi ... i'm using galaxy s3 gt i9300 and have been using cm11 for 6 months normally..
yesterday suddenly my phone was stuck at samsung screen ... i tried twrp to reinstall cm11 but when i tries to factory reset it fails and shows a bunch of errors like :
unable to mount system
unable to mount data
unable to mount storage .. etc
then i tried to install from micro sdcard but it shows 0mb same as internal storage..
i tried to flash cm11 via adb from pc but it also fails

can you help me ?

thanks

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