Help i just want to boot my mac!!!!!

(I’m korean so i can’t use english well. Sorry)

Last night i turn off my mac and this morning i just turn it on. But it doesn’t work. And it also turn on with boot camp window.

I was disconcerted so search google to turn my mac by macOS.

(i consult this site : https://mybstory.tistory.com/m/entry/맥-OS-X-부트로더-복구하기-윈도우만-보일-때)

it seems it works nice

but on the step6 when i write the command

turminal return Answer like this

(gpt add: unable to open device ‘/dev/disk0’: Resource busy)

then i cannot do anything after that answer

please help me😭😭