your English is fine, I think (well, I have to talk, I am German )
if you do your scarf in stochinette stitch (one row knit, one row purl) then it will curl. It will curl from the edges in on all 4 sides.
The amount of curl is different depending on the yarn, the needle size, the tension in the piece. But it will curl.
you can make the edges different (all knit stiches for a few stitches on each side and a few rows in beginning and end). A nice way is seed stich (one knit one purl - and then the opposite in the next row)
you can also make the scarf essentially with a back liner - a second scarf that you sew to the back. But that still does curl some (to a tube, lengthwise)...
there is a thread about stochinette stitch and curling:
maybe that gives you more information.
By the way: on some scarfs I love how it curls in a tube / rolls up - at least on the sides... not so much on the ends