Evening from Australia,
I need a few things to help answer your question better:
* What CPU does your computer have
* Tell me more about what is happening as many people do not know what device guard is. I use a thinkpad and didn't even know till i googled it
* Do you have a backup of your files?
If it's what i think it is like (A bitlocker style protection) you are SOL unless you change out your SSD.
If it's a type of kernel encryption (Like filevault on mac which encrypts the entire machine) SOL mate the board has to be changed.
If it's a windows thing you might be able to get away with a reinstall.
From a quick google, it would appear that maybe something else is active. Have a poke around the BIOS and play with some buttons (Not to the point you brick the computer)