how i can write this line in lite c?

while (players_health > 0)

same

up you write
var players_health = 100;
and then your code like
while(players_health < 100)
{
your function
}

hmm it doesnt work.. :-(

Error in Main line 154: 'players_health' undeclared identifier

<while(players_health < 100)
>

you have not defined a variable called players_health before. The engine does not know what players_health is.
TheLiam has already given you a solution for that.

you should work through the online tutorial if you don't know what that means.
Hint: There is also a german version of that tutorial.

Workshop number 2 is about your problem, they even show your error message there.

thank for your help. can you help me please with this line right here? sorry. but i are not a programmer :-(

player_speed.x = robot_speed * time_step;

we also need to see how you defined player_speed and robot_speed.
player_speed needs to be defined as a VECTOR so you can access the .x parameter.
Edit: Thats also something you should have already learned from the tutorial.