Still having trouble saving, loading from yml

I have searched on the forum quite a lot but still can't find a way to save stuff to yml file, in this case, coordinate.yml. So my question is how to save, RETRIEVE DATA FROM IT, and deleting it.
For example, the config have this data.
data:
playername:
- 0
- 12
- 823

So how would I write a code so that a new data is generated so that a player name is in there

Spoiler: Explanation if you didn't understand that

(kinda hard to explain, i mean how to create a new section like this:
anotherplayer:
- 123
- 234
- 345
)

and also how to write the code so that the value returns 823.
Finally, upon server stop, does the playerquitevent get triggered?

PHP:

$yml = new Config($this->getDataFolder().'coordinates.yml', Config::YAML);

$key = $player->getName(); // Steve
$yml->setNested($key, array($x, $y, $z));
$yml->getNested($key); // returns array of $x, $y and $z
// Remove key
$yml->remove($key);
// End of session
$yml->save();


This will return:
coordinates.yml

Code:

---[]
...

Yes an empty, because i removed that key after i set it.
But what would the file look like if i didnt?
coordinates.yml

Code:

---
Steve:
- 83
- 42
- 94
...

For the code part: search the forums.
For your grammar: you made two grammar mistakes in one sentence. It should be "For example, the config has these data."

Yes PlayerQuitEvent is triggered but there is no plugins that could Catch that event because plugins is disabled first.

Thanks! I will try that out soon.

I know, I'm not that great at grammar :/

Is there a possible workaround for it?