Tente isto: Comece no modo somente texto
Switch on your computer. Wait until the BIOS has finished loading, and press and hold Shift, which will bring up the Grub menu.
Select the line which starts with Advanced options.
Select the line ending with (recovery mode)
Press Return and your machine will begin the boot process.
After a few moments, your PC should display a menu with a number of options, including Drop to root shell prompt. Press Return with this option highlighted.
The PC will start in a terminal.
Execute estes comandos:
Montar partições no modo de leitura / gravação
mount -o remount,rw /
mount --all
Atualizar repositórios
apt update
Instalar o aptitude e o deborphan
apt install --reinstall aptitude deborphan
Elimine os componentes da unidade que não são necessários no gnome
aptitude remove '?and(?reverse-depends(unity),?not(?reverse-depends(?exact-name(gnome))))'
Reinstale o gnome
apt install --reinstall gnome
Eliminar pacotes órfãos
deborphan
apt --purge remove $(deborphan)
deborphan --libdevel
apt --purge remove $(deborphan --libdevel)
deborphan --find-config
dpkg --purge $(deborphan --find-config)
Remover pacotes desnecessários
apt autoremove
Remover pacotes baixados
apt clean
Reinicie o sistema
reboot