My phone won't boot up suddenly. Please help, thanks!

It is Samsung Galaxy Note 2 (GT-N7100), unrooted, stock ROM.
It always stuck at the Samsung Galaxy Note 2 logo screen.
I can boot to recovery mode and download mode.
What should I do to save my phone? Thanks a lot.

I tried to flash by using download mode but I got these errors.

< ID:0/003> Added!!
< ID:0/003> Odin engine v(ID:3.1205)..
< ID:0/003> File analysis..
< ID:0/003> SetupConnection..
< ID:0/003> Initialzation..
< ID:0/003> Get PIT for mapping..
< ID:0/003> Firmware update start..
< ID:0/003> SingleDownload.
< ID:0/003> sboot.bin
< ID:0/003> FAIL!
< ID:0/003>
< ID:0/003> Complete(Write) operation failed.
< OSM> All threads completed. (succeed 0 / failed 1)

When repartition is checked,

< ID:0/004> Added!!
< ID:0/004> Odin engine v(ID:3.1205)..
< ID:0/004> File analysis..
< ID:0/004> SetupConnection..
< ID:0/004> Initialzation..
< ID:0/004> Set PIT file..
< ID:0/004> DO NOT TURN OFF TARGET!!
< ID:0/004> Can't open the specified file. (Line: 1831)
< OSM> All threads completed. (succeed 0 / failed 1)

The following errors displayed when I booted to recovery mode:

Android system recovery < 3e >
KOT49H.N7100ZSUFNL1

E:failed to mount /efs (No such file or directory)
E:failed to mount /system ((No such file or directory))

# MANUAL MODE #
--Appling Multi-CSC
E:failed to mount /system (No such file or directory)
can't mount '/system' (No such file or directory)
E:failed to mount /cache (No such file or directory)
can't mount '/cache' (No such file or directory)
E:failed to mount /cache (No such file or directory)
E:can't mount /cache/recovery/last_recovery
E:failed to mount /data (No such file or directory)
E:can't mount /data/log/recovery_log.txt
E:failed to mount /system (No such file or directory)
E:failed to mount /cache (No such file or directory)
E:can't mount /cache/recovery/log
E:can't open /cache/recovery/log
E:failed to mount cache (No such file or recovery)
E:Can't mount /cache/recovery/last_log
E:can't open /cache/recovery/last_log
E:failed to mount /cache (No such file or recovery)
E:can't mount /cache/recovery/last_install
E:Can't open /cache/recovery/last_install
E:failed to mount /cache (No such file or recovery)

— modified on Mar 2, 2017, 6:50:09 AM