All scripts must be included before any manin code.
eg:

#include <acknex.h>
#include <default.c>
#include "instruct.c"

var speed = 50;
BMAP* mouse_pcx = blah blah blah

function main()
{
blah;
blah;
blah;
}

Where you have! level_load("choosechar.c");
You must specify a level.wmb NOT a script.
eg: level_load("main_game.wmb")