Yes exactly. I thought it would be cleaner if all partition are erased. After I ran the tool in download mode I had to restart manually. But then the system booted with no problems except missing IMEI. But then I unlocked my device and booted twrp. Then I restored my EFS backup. After that lock your device again or leave it unlocked. Then run *#268# (I think) and restored my EFS completely.
The download mode flashes all partitions (both slots as well). But it erases some too like the efs partition with your imei in it.
So to sum up (Sorry for being so annoying), you erased every partition (including efs) in fastboot and after that you ran the program in upgrade mode, and when the phone rebooted you were stuck in a bootloop (The red spinning circle thingy) without any possible way of restoring the phone, right?
Then you ran the tool in smt mode and when the tool finished, your phone was finally able to boot back to oxygenos (but with no efs).
Please tell if this is correct and if this restores every partition (including the critical ones).
Thanks a lot.