fold the paper so that 2 cm is left. cut at the half of the folded section, unfold, cut at the crease, and cut the remaining piece in half. That's 3 cuts, 60 seconds but the folding might take longer than just making 4 cuts.
2 cm per 10 cm can be cut into 5 pieces from a 10 per 10.
As you cut the strips, you need 4 cuts to make 5 strips so 80 seconds (not 5 cuts because once you make one cut there are 2 strips, 2 cuts - 3; 3 cuts - 4 and 4 cuts finally 5 strips)
from each sheet you get 5 strips of paper for this reason the elf will take 80 seconds. 20 seconds for the first strip, 20 for the second strip, 20 for the third strip and 40 for the fourth and fifth strip.
It only needs 40 seconds by folding it into one 2 x 10 cm folded strip into inside (folding one way). 20 seconds to cut from inside to outside of folds into right side, and 20 seconds into left side. So the elf needs 40 seconds to cut paper completely into strips.