ok now I'm writing another program...I'm working with strings I'll post it when I'm finished. By the way: i know my comments are quite bad,but it's because you don't have the image of my robot...the problem is that the angles that I write aren't the same as the one of the servo (there is a ~5° difference) 
Thank you for the problem with long-float, I hadn't noticed, I'll fix it now.
For the problem with the sending code i've attached it to my third comment (it was with the second one but somenthing hasn't worked)
And for the last problem:I had changed this part of my code but i wanted not to save those changes, but when i've closed arduino i might have saved them by mistake, sorry
Maybe is better just to start with a new code, so it'll be easier for you to help me: I have had a new idea:I "pack" a string with all the data,i send it trough the xbees and than unpack it.
the idea was a string like that: "ST;z=***x=***y=***END", where *** can be numers from 0 to 255. I packed it succesfully and seems to work. now I have to unpack it. the two programs are attached
ctrl_xbee_usbcom_v1_2.ino (1.05 KB)
ctrl_xbee_usbcom_send.ino (731 Bytes)