But i really need to get a weight measurement. That is not in a graph.
First "catch your rabbit".
When you have your load cell and op-amp, etc working nicely, producing a voltage that swings reasonably well, but stays between 0 and 5v (or 0 and 3.3v, if you have a 3.3v Arduino), you're virtually done. (Feed that into an Arduino analog input, display the reading. You can then, with no programming skills, make up an ink-on-paper conversion chart by testing your tool with some known weights. It takes very little programming to put that chart and the look up "inside" the Arduino.
But first you need that "rabbit".
Yeah I will catch my "rabbit" but can i ask something. Do you have any sample codes?
Or any tutorial for me how can i work with load cell?