Why does that not work

PHP:

/**
  * @param BlockBreakEvent $event
  */
  public function onPlayerBreakBlock(BlockBreakEvent $event){
  if ($event->getBlock()->getID() == Item::SIGN || $event->getBlock()->getID() == Item::WALL_SIGN || $event->getBlock()->getID() == Item::SIGN_POST) {
  $signt = $event->getBlock();
  if (($tile = $signt->getLevel()->getTile($signt))){
  if($tile instanceof Sign) {
  if(strtolower(trim($signt->getLine(0))) == "status" || strtolower(trim($signt->getLine(0))) == "[status]"){
  if ($event->getBlock()->getX() == $this->sign->getNested("sign.x") || $event->getBlock()->getY() == $this->sign->getNested("sign.y") || $event->getBlock()->getZ() == $this->sign->getNested("sign.z")) {
  if($event->getPlayer()->hasPermission("signstatus.break")) {
  $this->sign->setNested("sign.x", $event->getBlock()->getX());
  $this->sign->setNested("sign.y", $event->getBlock()->getY());
  $this->sign->setNested("sign.z", $event->getBlock()->getZ());
  $this->sign->setNested("sign.enabled", false);
  $this->sign->setNested("sign.level", "world");
  $this->sign->save();
  $this->sign->reload();
  $event->getPlayer()->sendMessage($this->prefix.$this->translation->get("sign_destroyed"));
  }else{
  $event->getPlayer()->sendMessage($this->prefix.$this->translation->get("sign_no_perms"));
  $event->setCancelled();
  }
  }
  }
  }
  }
  }
  }


Error: Call to undefined method pocketmine\block\WallSign::getLine()
The error is on if(strtolower(trim($signt->getLine(0))) == "status" || strtolower(trim($signt->getLine(0))) == "[status]"){

$signt must be a tile, so use

PHP:

$this->getServer()->getLevelByName("level")->getTile(new Vector3($event->getBlock()->getX(), $event->getBlock()->getY(), $event->getBlock()->getZ()));

Who told you to use Server::getInstance()??

Now it's
Fatal error: Call to undefined method pocketmine\tile\Sign::getLine() in G:\Daten_Schnell\Tim\PocketServerTest\plugins\SignStatusV2.2.1-FIXload9099\src\SignStatus\SignStatus.php on line 145

OK

Fatal error: Call to undefined method pocketmine\tile\Sign::getLine() in G:\Daten_Schnell\Tim\PocketServerTest\plugins\SignStatusV2.2.1-FIXload9099\src\SignStatus\SignStatus.php on line 145
when using
it as tile

PHP:

$text = Sign::getText();
$text[0]; // Line1 etc.

Why do you search a level by name while you already have the level object from the block?

PHP:

  public function onPlayerBreakBlock(BlockBreakEvent $event){
  if ($event->getBlock()->getID() == Item::SIGN || $event->getBlock()->getID() == Item::WALL_SIGN || $event->getBlock()->getID() == Item::SIGN_POST) {
  $signt = $event->getBlock();
  if (($tile = $signt->getLevel()->getTile($signt))){
  if($tile instanceof Sign) {
  if(strtolower(trim($signt->getLevel()->getTile($signt)->getText(0))) == "status" || strtolower(trim($signt->getLevel()->getTile($signt)->getText(0))) == "[status]"){
  if ($event->getBlock()->getX() == $this->sign->getNested("sign.x") || $event->getBlock()->getY() == $this->sign->getNested("sign.y") || $event->getBlock()->getZ() == $this->sign->getNested("sign.z")) {
  if($event->getPlayer()->hasPermission("signstatus.break")) {
  $this->sign->setNested("sign.x", $event->getBlock()->getX());
  $this->sign->setNested("sign.y", $event->getBlock()->getY());
  $this->sign->setNested("sign.z", $event->getBlock()->getZ());
  $this->sign->setNested("sign.enabled", false);
  $this->sign->setNested("sign.level", "world");
  $this->sign->save();
  $this->sign->reload();
  $event->getPlayer()->sendMessage($this->prefix.$this->translation->get("sign_destroyed"));
  }else{
  $event->getPlayer()->sendMessage($this->prefix.$this->translation->get("sign_no_perms"));
  $event->setCancelled();
  }
  }
  }
  }
  }
  }
  }


That doesn't work, too:
2015-12-19 [08:32:26] [CRITICAL]: "Could not pass event 'pocketmine\event\block\BlockBreakEvent' to 'SignStatus v2.1': trim() expects parameter 1 to be string, array given on SignStatus\SignStatus
2015-12-19 [08:32:26] [WARNING]: InvalidArgumentException: "trim() expects parameter 1 to be string, array given" (E_WARNING) in "/SignStatusV2.2.2/src/SignStatus/SignStatus" at line 145

Still need help here...

Sign::getText() returns an array, you can't do Sign::getText(0)! Learn something about arrays.

Did never understand arrays
Can anyone show me a code of that if function?

I did show you a code, and you liked it.

HTTPS://PHP.net/arrays

Excuse me:
1. What sense are you trying to make? It is the return value not the parameter that is array. The function has void parameters.
2. Block::Sign? Excuse me, are you speaking in PHP?

That code still still not works...
I am getting more and more confused...

What code do you use now?

That:

PHP:

  /**
  * @param BlockBreakEvent $event
  */
  public function onPlayerBreakBlock(BlockBreakEvent $event){
  if ($event->getBlock()->getID() == Item::SIGN || $event->getBlock()->getID() == Item::WALL_SIGN || $event->getBlock()->getID() == Item::SIGN_POST) {
  $signt = $event->getBlock();
  if (($tile = $signt->getLevel()->getTile($signt))){
  if($tile instanceof Sign) {
  if(strtolower(trim($signt->getLevel()->getTile($signt)->getText(0))) == "status" || strtolower(trim($signt->getLevel()->getTile($signt)->getText(0))) == "[status]"){
  if ($event->getBlock()->getX() == $this->sign->getNested("sign.x") || $event->getBlock()->getY() == $this->sign->getNested("sign.y") || $event->getBlock()->getZ() == $this->sign->getNested("sign.z")) {
  if($event->getPlayer()->hasPermission("signstatus.break")) {
  $this->sign->setNested("sign.x", $event->getBlock()->getX());
  $this->sign->setNested("sign.y", $event->getBlock()->getY());
  $this->sign->setNested("sign.z", $event->getBlock()->getZ());
  $this->sign->setNested("sign.enabled", false);
  $this->sign->setNested("sign.level", "world");
  $this->sign->save();
  $this->sign->reload();
  $event->getPlayer()->sendMessage($this->prefix.$this->translation->get("sign_destroyed"));
  }else{
  $event->getPlayer()->sendMessage($this->prefix.$this->translation->get("sign_no_perms"));
  $event->setCancelled();
  }
  }
  }
  }
  }
  }
  }


It crashes...

Did you even read my code and my reply?!

so $text[0] holds the contents of the line1 on sign?