Koraks, I don't see any double lines, even in the cropped section you posted. If there are double lines, that, indeed, points to movement. A popping negative or bumping the enlarger or jiggling it during exposure will certainly cause those.
I assumed, maybe incorrectly, that the OP had made more than one print and had simply posted a representative sample.
OP, if you just made one print, make some more, being careful with focusing and not to bump or move the enlarger during exposure. Also, heat up the negative using the focus setting for a while right before the exposure to get the negative "popped" (if that is the problem), so it doesn't during exposure and then report back.
Doremus