at the moment I\'m coding a little app with SpriteKit, which works perfectly fine, but the only problem is an SKLabelNode, which I initialize with the following normal piece
Actually, you don't need to preload the font for an SKLabelNode. The delay is caused by the fact that you're using the wrong font name. There's no "Futura" font on iOS - what you probably mean is "Futura-Medium". Replace "Futura" with "Futura-Medium", and you should see the load time drastically fall.
(You can still preload your fonts, but it's not necessary; lazy loading is pretty fast provided you use a correct font name.)