Possible override for black screen after changing the gpu?

I recently installed Ubuntu схвати I need to learn Фортран. Meanwhile I bought new GPU - r7 370. When I installed it into motherboard and started Убунту I was greeted with black screen, I think that system loaded but didn't шоу anything.

I tried to install some драйверы but the result was the same, I only could get to Ubuntu путь integrated gpu.

Anyhow, I managed to go around this problem, but I don't understand why and how: After getting into grub I go into recovery mode and there... I just обобщает, что нормальный booting sequence by прессинг "обобщает". And now гm here in Ubuntu writing this. Any разрабатывает why this happens? Any разрабатывает how to make this permanent, instead of following those few steps every украдите I need to power up this system?