Well, thanks u guys for the good feedbacks and tips
There's another actor that creates the blocks. It has an animation with, let's say, 2 frames.
It's located about 100 pixels left of the view. It's:
Animation finish -> create actor -> block -> relative to creator
For the block goes:
Create actor -> y = rand(//top limit) - (//bottom limit);
xvelocity = -10;
It's actually not the guy who walks, but the blocks, the ground and the stuff.