Unmountable Boot Volume Error among other things

Hello,

I started having issues with my laptop yesterday. It would load, I'd sign in and then it would freeze. I ended up finally being able to reset my windows but kept all of my files (I'm a photographer, a few new sessions weren't backed up). It worked well, I was able to backup my files today but was still experiencing the freezing. I freed up all of the space I could (about 260 GB out of 450 GB but still freezing!!! So, I decided to do a restart and see if that would help. Now I'm getting this damn error! I can't bring up the F12 menu to boot from disc. I can't do anything :( I'm freaking out!!! I have so much editing to do. Please help me!!! I've read so many articles and such but nothing has been my exact issue so nothing worked.

2 year old laptop, Lenovo, Windows 8 updated to Windows 10 months ago (clean install).