You're wrong that you got nothing in these forums.
First, you got some helpful links to learn from.
And next, I gave you everything you need

Target (if you search the manual) defines coordinates after a c_trace or other functions (c_trace is what you need in the example) , vec_for_screen you need to convert the screen coordinates. Everything else you can learn in the first tutorials...
Not tested, but here's what I mean:
function player_act()
{
var tempcoord[3];
var tempcoord2[3];
while(1)
{
if(mouse_left == 1)
{
tempcoord[0] = mouse_pos.x; // get pos infront of camera
tempcoord[1] = mouse_pos.y;
tempcoord[2] = 0;
vec_for_screen(tempcoord[0],camera);
tempcoord2[0] = mouse_pos.x; // get pos far from camera
tempcoord2[1] = mouse_pos.y;
tempcoord2[2] = 5000;
vec_for_screen(tempcoord2[0],camera);
c_trace(tempcoord[0], tempcoord2[0], USE_POLYGON ); // trace between the two positions
if(result > 0) // if trace hit
{
if(vec_dist(my.x, target.x) > 40) // if distance from player is more than 40 quants
{
vec_set(tempcoord[0], target.x); // get my target direction
vec_sub(tempcoord[0], my.x);
vec_to_angle(my.pan, tempcoord[0]); // rotate me to my target
my.tilt = 0;
my.roll = 0;
c_move(me, vector(10 * time_step, 0, 0), nullvector, IGNORE_PASSABLE | GLIDE ); // move me towards target
}
}
}
wait(1);
}
}
With some while statements (for example while(vec_dist() > 40) ) you can make the player go without holding mouse_left, or combine both methods into one.
So, dont you agree I gave you everything in my first post? You just need to look in the manual about the needed functions, that I posted about.

I have 14 years of experience and I never remember what the functions need as parameters, I constantly go through the manual...You just need to memorize what functions are available...It takes time.
PS.: I'm still new to Lite-C, but this example is identical to my implementation, wich runs without errors. I dont know yet how to define a VECTOR so I used a var in my example. I think c_trace, c_move and vec_for_screen should be the same as in Lite-C...