So I finally got the first package with my new parts.
Including:
*New belt for my CS Setup (156T instead of 158 default on rear)
*New Square Tamiya TA05-VDF Tensioner Flange Bearings. I definately like them already, even though my new belt is tighter, it still helps a lot to hold the belt in place. Results in a nicer and smoother drive - For ~7€ definately worth it! ATTENTION: it's just for ONE tensioner. If you want both tensioners with the square bearings, you need to order 2! But I just put them on the first tensioner (near the middle).