Unfortunately some data was downloading and my Mac got stuck, so I forcefully power it off. After that, I couldn't enter the login screen, because the loading bar was stuck.
I tried to enter safe mode, but with no success. After that, I entered single user mode and entered some command to repair disk, but it scanned for 10 minutes and failed.
I finally managed to enter recovery/repair mode with Disk Utility (previously no disk was listed in menu), and clicked 'First Aid'. This failed after one second with something like 'invalid node'. I Googled some time and entered Terminal in recovery mode and entered this command that many people praised, but I got this:
-bash-3.2# /sbin/fsck_hfs -yprd /dev/disk0s2 /dev/rdisk0s2: starting Unable to open block device /dev/disk0s2: Resource busyjournal_replay(/dev/disk0s2) returned 16 /dev/rdisk0s2: ** /dev/rdisk0s2 (NO WRITE ACCESS) /dev/rdisk0s2: UNEXPECTED INCONSISTENCY; RUN fsck_hfs MANUALLY. -bash-3.2#