Format the internal storage of Nexus 5

My nexus 5 was dying probably because of errors on the internal storage.
(OTA upgrade failed because the downloaded file was broken, or WiFi did not work at all and died with OS.)
I almost gave up, but in the end I realize that TWRP recovery enables me to format the internal storage.
I have just tried and now it is working with WiFi.

Unfortunately, I have already bought a Xiaomi Redmi Note3 pro.
I will keep it for my friends' coming.