what do think that I've to do ( I can't bring back the LCD because I buy it a long time a go) ??
I think you need to post some pictures of the chassis (hopefully fully assembled - with battery holder, motors, and other things in place), the arduino, and the LCD - preferably all together, near each other (as well as separate), perhaps along with some kind of measuring device in the photos, so we can all tell what is what, sizes, etc - in relationship to each other - in order to provide you with potential solutions. Otherwise, we'll all just be making guesses.
Depending on what the chassis is/looks like - you'll likely either need to extend it (up or "out") to make some room, and/or you'll need to use some standoffs or brackets to place the LCD in a different position above or around the Arduino in some manner.