You say that booting into safe mode is possible, therefore I presume before you get there you can see the 'Boot options' screen.
Have you tried selecting either 'Last known good configuration' ( 1st choice ) or 'System repair' ( 2nd choice ) ? The first choice is the simpler, because all you have to do is select it and let it do its thing ! System repair is a bit more complicated, but allows more options. If it works, great. If it doesn't, choose 'Advanced options', then 'System restore' and see if you can restore the computer to a restore point dating from before this trouble started.
This often works, but not always. Nothing works all the time ! If it doesn't, it is probably tiime to check your hard drive for problems before going any further.