Manipulation of variables

I face a problem that i can't seem to resolve.

For more manageable  mod I should change a global variable's type to int array. I have added my variable as player lifetime double and after this I have managed to open the variables section in mcreator (as the source code) and i have made the following changes: 

private static class PlayerVariablesStorage implements Capability.IStorage<PlayerVariables> {
		@Override
		public INBT writeNBT(Capability<PlayerVariables> capability, PlayerVariables instance, Direction side) {
			CompoundNBT nbt = new CompoundNBT();
nbt.putIntArray("Proficiencies", instance.Proficiencies);
			return nbt;
		}
@Override
		public void readNBT(Capability<PlayerVariables> capability, PlayerVariables instance, Direction side, INBT inbt) {
			CompoundNBT nbt = (CompoundNBT) inbt;
instance.Proficiencies = nbt.getIntArray("Proficiencies");
		}
	}
public static class PlayerVariables {
public int[] Proficiencies = new int[50];
		public void syncPlayerVariables(Entity entity) {
			if (entity instanceof ServerPlayerEntity)
				MinecraftMod.PACKET_HANDLER.send(PacketDistributor.PLAYER.with(() -> (ServerPlayerEntity) entity),
						new PlayerVariablesSyncMessage(this));
		}

But my procedures and everything else throws an error at me about "Proficiencies can not be converted to int[]".

What did i do wrong or how can i fix this?