El Capitan Ruined My Macbook Pro

As everyone else, i was excited to upgrade my Macbook's OS but after doing so, it appeared to be the worst mistake i have made in my life!

After installation, mac mac couldn't boot!

Apple logo with a stuck progress bar was all what is there!

I left it for hours but it never progressed!

I did clean installation 4 times with the same issue and while i am writing this, i am trying internet recovery again !!

my laptop is 2011 Macbook Pro with 750 GBs HDD and 8 GBs RAM!

NOw all what i wanna do is downgrade to Yosemite as this seems to me as a big faliure!

I did reset pram, reset Smc, reset nvram with no luck.

SAfe mode doesn't boot

Bootable USB doesn't open ( though it did only one time, after the installation MAC starts working then FileVault appear i tried to switch it off, it refused then the mac shut down and never booted again)

i can't open disk utility as it gives my white screen only!

i am on this since 2 days!

ANy advise?