You may want to create a bootable external drive so you can boot up under it to do a full wipe and install onto the internal SSD as that's about all that's left if the boot blocks are damaged. Otherwise it's time for a new SSD. Luckily OWC produced a pin compatible drive [https://eshop.macsales.com/shop/ssd/owc/macbook-pro-13-inch-non-touch-bar/2016-2017|13-inch MacBook Pro non-Touch Bar (2016 - 2017)]