diff --git a/src/pocketmine/Player.php b/src/pocketmine/Player.php
index 77de5256f..e2e228c8f 100644
--- a/src/pocketmine/Player.php
+++ b/src/pocketmine/Player.php
@@ -1641,7 +1641,7 @@ class Player extends Human implements CommandSender, InventoryHolder, ChunkLoade
 
 		$this->achievements = [];
 
-		/** @var Byte $achievement */
+		/** @var ByteTag $achievement */
 		foreach($nbt->Achievements as $achievement){
 			$this->achievements[$achievement->getName()] = $achievement->getValue() > 0 ? true : false;
 		}
diff --git a/src/pocketmine/entity/Attribute.php b/src/pocketmine/entity/Attribute.php
index 62b9b6916..f6fb4b238 100644
--- a/src/pocketmine/entity/Attribute.php
+++ b/src/pocketmine/entity/Attribute.php
@@ -56,9 +56,9 @@ class Attribute{
 		self::addAttribute(self::KNOCKBACK_RESISTANCE, "generic.knockbackResistance", 0.00, 1.00, 0.00);
 		self::addAttribute(self::HEALTH, "generic.health", 0.00, 20.00, 20.00);
 		self::addAttribute(self::MOVEMENT_SPEED, "generic.movementSpeed", 0.00, 340282346638528859811704183484516925440.00, 0.10);
-		self::addAttribute(self::FOLLOW_RANGE, "generic.followRange", 0.00, 2048.00, 16.00);
+		self::addAttribute(self::FOLLOW_RANGE, "generic.followRange", 0.00, 2048.00, 16.00, false);
 		self::addAttribute(self::HUNGER, "player.hunger", 0.00, 20.00, 20.00);
-		self::addAttribute(self::ATTACK_DAMAGE, "generic.attackDamage", 0.00, 340282346638528859811704183484516925440.00, 1.00);
+		self::addAttribute(self::ATTACK_DAMAGE, "generic.attackDamage", 0.00, 340282346638528859811704183484516925440.00, 1.00, false);
 		self::addAttribute(self::EXPERIENCE_LEVEL, "player.level", 0.00, 24791.00, 0.00);
 		self::addAttribute(self::EXPERIENCE, "player.experience", 0.00, 1.00, 0.00);
 	}
@@ -199,7 +199,7 @@ class Attribute{
 		return $this->shouldSend and $this->desynchronized;
 	}
 
-	public function markSynchronized(){
-		$this->desynchronized = false;
+	public function markSynchronized(bool $synced = true){
+		$this->desynchronized = !$synced;
 	}
 }
diff --git a/src/pocketmine/entity/Effect.php b/src/pocketmine/entity/Effect.php
index 56f4ff660..c6f2e17d3 100644
--- a/src/pocketmine/entity/Effect.php
+++ b/src/pocketmine/entity/Effect.php
@@ -250,7 +250,7 @@ class Effect{
 		$this->color = (($r & 0xff) << 16) + (($g & 0xff) << 8) + ($b & 0xff);
 	}
 
-	public function add(Entity $entity, $modify = false){
+	public function add(Entity $entity, $modify = false, Effect $oldEffect = null){
 		if($entity instanceof Player){
 			$pk = new MobEffectPacket();
 			$pk->eid = 0;
@@ -270,6 +270,24 @@ class Effect{
 		if($this->id === Effect::INVISIBILITY){
 			$entity->setDataFlag(Entity::DATA_FLAGS, Entity::DATA_FLAG_INVISIBLE, true);
 			$entity->setDataProperty(Entity::DATA_SHOW_NAMETAG, Entity::DATA_TYPE_BYTE, 0);
+		}elseif($this->id === Effect::SPEED){
+			$attr = $entity->getAttributeMap()->getAttribute(Attribute::MOVEMENT_SPEED);
+			if($modify and $oldEffect !== null){
+				$speed = $attr->getValue() / (1 + 0.2 * $oldEffect->getAmplifier());
+			}else{
+				$speed = $attr->getValue();
+			}
+			$speed *= (1 + 0.2 * $this->amplifier);
+			$attr->setValue($speed);
+		}elseif($this->id === Effect::SLOWNESS){
+			$attr = $entity->getAttributeMap()->getAttribute(Attribute::MOVEMENT_SPEED);
+			if($modify and $oldEffect !== null){
+				$speed = $attr->getValue() / (1 - 0.15 * $oldEffect->getAmplifier());
+			}else{
+				$speed = $attr->getValue();
+			}
+			$speed *= (1 - 0.15 * $this->amplifier);
+			$attr->setValue($speed);
 		}
 	}
 
@@ -286,6 +304,12 @@ class Effect{
 		if($this->id === Effect::INVISIBILITY){
 			$entity->setDataFlag(Entity::DATA_FLAGS, Entity::DATA_FLAG_INVISIBLE, false);
 			$entity->setDataProperty(Entity::DATA_SHOW_NAMETAG, Entity::DATA_TYPE_BYTE, 1);
+		}elseif($this->id === Effect::SPEED){
+			$attr = $entity->getAttributeMap()->getAttribute(Attribute::MOVEMENT_SPEED);
+			$attr->setValue($attr->getValue() / (1 + 0.2 * $this->amplifier));
+		}elseif($this->id === Effect::SLOWNESS){
+			$attr = $entity->getAttributeMap()->getAttribute(Attribute::MOVEMENT_SPEED);
+			$attr->setValue($attr->getValue() / (1 - 0.15 * $this->amplifier));
 		}
 	}
 }
diff --git a/src/pocketmine/entity/Entity.php b/src/pocketmine/entity/Entity.php
index eab6b1e49..e386379e6 100644
--- a/src/pocketmine/entity/Entity.php
+++ b/src/pocketmine/entity/Entity.php
@@ -319,7 +319,11 @@ abstract class Entity extends Location implements Metadatable{
 	}
 
 	public function setSprinting($value = true){
-		$this->setDataFlag(self::DATA_FLAGS, self::DATA_FLAG_SPRINTING, (bool) $value);
+		if($value !== $this->isSprinting()){
+			$this->setDataFlag(self::DATA_FLAGS, self::DATA_FLAG_SPRINTING, (bool) $value);
+			$attr = $this->attributeMap->getAttribute(Attribute::MOVEMENT_SPEED);
+			$attr->setValue($value ? ($attr->getValue() * 1.3) : ($attr->getValue() / 1.3));
+		}
 	}
 
 	/**
@@ -363,7 +367,7 @@ abstract class Entity extends Location implements Metadatable{
 			){
 				return;
 			}
-			$effect->add($this, true);
+			$effect->add($this, true, $oldEffect);
 		}else{
 			$effect->add($this, false);
 		}
@@ -408,10 +412,10 @@ abstract class Entity extends Location implements Metadatable{
 	}
 
 	/**
-	 * @param int|string $type
-	 * @param FullChunk  $chunk
-	 * @param CompoundTag   $nbt
-	 * @param            $args
+	 * @param int|string  $type
+	 * @param FullChunk   $chunk
+	 * @param CompoundTag $nbt
+	 * @param             $args
 	 *
 	 * @return Entity
 	 */
@@ -506,6 +510,17 @@ abstract class Entity extends Location implements Metadatable{
 	protected function initEntity(){
 		assert($this->namedtag instanceof CompoundTag);
 
+		if(isset($this->namedtag->CustomName)){
+			$this->setNameTag($this->namedtag["CustomName"]);
+			if(isset($this->namedtag->CustomNameVisible)){
+				$this->setNameTagVisible($this->namedtag["CustomNameVisible"] > 0);
+			}
+		}
+
+		$this->scheduleUpdate();
+
+		$this->addAttributes();
+
 		if(isset($this->namedtag->ActiveEffects)){
 			foreach($this->namedtag->ActiveEffects->getValue() as $e){
 				$effect = Effect::getEffect($e["Id"]);
@@ -518,18 +533,6 @@ abstract class Entity extends Location implements Metadatable{
 				$this->addEffect($effect);
 			}
 		}
-
-
-		if(isset($this->namedtag->CustomName)){
-			$this->setNameTag($this->namedtag["CustomName"]);
-			if(isset($this->namedtag->CustomNameVisible)){
-				$this->setNameTagVisible($this->namedtag["CustomNameVisible"] > 0);
-			}
-		}
-
-		$this->scheduleUpdate();
-
-		$this->addAttributes();
 	}
 
 	protected function addAttributes(){
@@ -1559,6 +1562,7 @@ abstract class Entity extends Location implements Metadatable{
 	 * @param int  $propertyId
 	 * @param int  $id
 	 * @param bool $value
+	 * @param int  $type
 	 */
 	public function setDataFlag($propertyId, $id, $value = true, $type = self::DATA_TYPE_BYTE){
 		if($this->getDataFlag($propertyId, $id) !== $value){