System wiped - Bootloop

Hello,
I deleted from TWRP the system partition and now the device can go only in TWRP 3.0.2-2
or in download mode where I see:

ODIN MODE
PRODUCT NAME: SM-G900F
CURRENT BINARY: Custom
SYSTEM STATUS: Custom
REACTIVATION LOCK: OFF
KNOX WARRANTY VOID: 0x1 (4)
QUALCOMM SECUREBOOT : ENABLE (CSB)
SECURE DOWNLOAD: ENABLE
UDC START

What can I do?

Thanks!