Welcome as long as you understand why it works and why it didn't before which is what the Great Kartoffel, was telling you.

Keep coding and keep learning, btw Welcome to 3dgs

And, you might want to increment/decrement with "time_step / 16", and wait(1) (1 frame). Otherwise, your function stops for 1 second (wait(-1)) and runs again... With time_step / 16 your function runs with the frames per second speed.

Not that its vital for a flashlight, but sometimes you might want to do other stuff around that if statement, that has to run more times per second...so use wait(-1) only when its trivial.

Nur damit ich das richtig verstanden habe. Wenn ich sowas hier habe:

while(1){

if(key_f) Funktion();

wait(1);
}

Dann wird die function Funktion jeden Frame ausgelöst, weil es in einer Schleife mit wait(1) steht. Bei einer fps von 60 wird die Funktion also 60 mal in der Sekunde ausgelöst. Wenn ich also kurz auf die F-Taste drücke, sagen wir mal (1/20 Sekunden gedrückt) dann wird die Funktion (60/20) 3mal parallel durchgeführt und deshalb sinkt der Countdown schneller.

ISt das so ungefähr verstanden?

You understand perfectly- Remember to use a key_lock of some type because the very person will hold the key longer then 1 cycle.
BTW wait(1) is a frame not a time measure - it changes a bit for each cycle - however in your example of 60 fps then you are perfectly correct.

As a personal note, the new users who learn the fastest and best are people like you who want to understand the logic not just be hand a piece of code. My complements to you for start on a good foot.

@Malice
Thank you for your opinion. I will give my best