First, use 'code' tags when you post code. Now, the problem is really that computers are fast. Your while-loop above executes very quickly, so you only see the start (before the loop) and the end (after the loop has finished). Everything in between happens too quickly for you to see. One possibility is to insert a delay into the loop; you can use the Greenfoot.delay(...) method for this (look it up in the documentation). However, it's quite possible that you don't really need the while-loop at all. When your scenario runs, the 'act' method for each actor gets called repeatedly anyway, inside an "implicit" loop. It's usual for your actor to take only one "step" each time that act is called. You could do this by chaning the 'while' to an 'if' statement.

Thank you davmac, thats so logic.. I'm a amateur, thats why i have noobie codes xDD