Internal hard disk won't wipe, can't reinstall OS because not enough disk space
If you don't want retrieve your personal datas (I suppose they are saved) you can erase the entire disk and after reinstall Mac Os X. I suppose you have an usb key or an apple installer for install your Mac os system.
I refer to this : https://imgur.com/C5yYVeT
The command in the terminal is :
diskutil erasedisk apfs &quot;Alex HD&quot; gpt disk0

This will reinitialise the 128 Go SSD with an APFS Volume named Alex HD