Upset with the quality AND that last panel is that part of the chapter you just left untranslated?
As for time difference. Yeah when they don't explain I can understand the confusion. Basically from other works I've read the worlds are in different planes or dimensions. So 1 year in this home world was actually 1000 years in the immortal world.
Hopefully further down author don't mess it up. Like say he returns in a year but only 1 year passed in immortal world instead of 1000 supposed to.