Christian, I personally thought those looked pretty good! Why don't you throw some weight on the bar, then we can really see your deficiencies. I think you are sandbagging a little at 40kg.
Get yourself up to a decent working weight my friend. I found for myself, 155lbs is a good working weight. Of course, my form isn't perfect every rep with this weight, but when I am properly warmed up I rarely miss at 155lbs. Therefore, it is a good working weight to practice form with.