Sorry. All good. . I have improved my English skills. I have improved on my English skills, of last year. ....my English skills have improved. - ok, good to improve on something, is generally to better it, as in better than it, replace it with a better one. (Not make something better than it was before) So, not so obvioius to use on something that you actually evolve, in situ, as in alter the existing one. . This is last year's design. Today we show a design that improves on that design. This is last year's design. We have improved it. I have improved on the methods I used. My English skilld are improved. My English skills are much improved. >>I just feel weird because skills don’t improved by themselves but be someone or something like practicing. I have no sense of this aspect being involved. :)