i found my problem if anyone cares...

its the tyre friction i set it to 120...
if you want to correct it please add this code to Tank_Move function:

if(key_cud == 0 && key_cuu == 0) || (key_cud == 1 && key_cuu == 1)
{
vec_set(motor1,vector(0,0,0));
vec_set(motor2,vector(0,0,0));
}

if(key_cur == 0 && key_cul == 0)|| (key_cur == 1 && key_cul == 1)
{
vec_set(motor1,vector(0,0,0));
vec_set(motor2,vector(0,0,0));
}

if(key_cuu)
{
phent_setfriction(l_wheel1,230);
phent_setfriction(l_wheel2,230);
phent_setfriction(l_wheel3,230);
phent_setfriction(r_wheel1,230);
phent_setfriction(r_wheel2,230);
phent_setfriction(r_wheel3,230);

vec_set(motor1,vector(-1000,800,0));
vec_set(motor2,vector(-1000,800,0));
}

if(key_cud)
{
phent_setfriction(l_wheel1,230);
phent_setfriction(l_wheel2,230);
phent_setfriction(l_wheel3,230);
phent_setfriction(r_wheel1,230);
phent_setfriction(r_wheel2,230);
phent_setfriction(r_wheel3,230);

vec_set(motor1,vector(1000,800,0));
vec_set(motor2,vector(1000,800,0));
}





if(key_cur)
{
phent_setfriction(l_wheel1,40);
phent_setfriction(l_wheel2,40);
phent_setfriction(l_wheel3,40);
phent_setfriction(r_wheel1,40);
phent_setfriction(r_wheel2,40);
phent_setfriction(r_wheel3,40);

vec_set(motor1,vector(1000,800,0));
vec_set(motor2,vector(-1000,-800,0));
}

if(key_cul)
{
phent_setfriction(l_wheel1,40);
phent_setfriction(l_wheel2,40);
phent_setfriction(l_wheel3,40);
phent_setfriction(r_wheel1,40);
phent_setfriction(r_wheel2,40);
phent_setfriction(r_wheel3,40);

vec_set(motor1,vector(-1000,-800,0));
vec_set(motor2,vector(1000,800,0));
}