-Go to Recovery mode
-Enable network (so you have internet connection)
-Go to Root option (Recovery mode)
-When you are in terminal delete lightdm type without brackets {sudo apt-get remove --purge lightdm}
-Then type without brackets {sudo apt-get install lightdm} (wait to install it)
-Then type without brackets {sudo service lighdm start}
-When it's finished type exit (you will get back to Recovery console)
-Then go on third option dpkg (Repair broken packages)(confirm with Y)
-When it's finished with installing packages type without brackets {sudo reboot}
راستی سایت amd که تحریم کرده کسی میتونه پکیج درایورشو برام پیدا کنه lspci | grep ATI زدم به نظر به این نیاز داره Radeon HD 8570A/8570M کسی داره؟