Guys, please help, I managed to screw up my system just by rebooting into Ubuntu once to check some settings. I don't really know much about dual boot, and installing Ubuntu in parallel to my already working Mac worked well, multiple reboots, various updates to Ubuntu, always stayed on the background, and whenever I needed, I just use F12->Ubuntu(dedicated SSD drive) just for that.
Right now what happened is that after I reboot, I go with default boot options which is suppose to be my Mac, press ENTER, and, to my surprise dive directly into Ubuntu. I thought I've made a mistake, tried again, same thing.
I disconnected my Ubuntu SSD completely, the Ubuntu option to boot is still there, next to my Mac's drive option. I select Mac, and my computer goes into reboot mode automatically.
I booted with my rescue USB now, look at the content of EFI on my Mac, and there's ubuntu subfolder right next to OC and Boot. What a hack is it doing on my Mac drive? What changed it, because until last reboot, it wasn't there.
In any case, I can't boot without my rescue USB, and some of the parameters are outdated on it.
Please help, what's going on here.