@nenik has already fixed your ordering, two while loops, and curly braces. Here are two other comments:
Normally you would put
using namespace vex;
vex::brain Brain;
vex::motor Backleftmotor (vex::PORT1, vex::gearSetting::ratio18_1, true);
vex::motor Backrightmotor (vex::PORT2, vex::gearSetting::ratio18_1, true);
inside robot-config.h instead. This may not matter here, but sometimes it definitely matters. For example, you won’t get to the utility for the vision sensor through here, but through robot-config.h instead.
Also, the whole point of
using namespace vex;
is that you can avoid typing “vex::” everywhere. It’s slightly risky, but probably inconsequentially. But if you aren’t even going to use it (you’ve typed “vex::” everywhere), then why even include it?