I've been using Pi-hole on a 2014 Pi 2b successfully for many years with my PlusNet Hub Two router but have upgraded to a full fibre connection with Zen Internet. Speeds are great. Unfortunately I haven't been able to configure my FRITZ!Box 7530 router to work with Pi-hole.
I would be grateful if anyone has succeeded and could post some instructions in English
Please don't resurrect topics four years old that are only vaguely related to your issue and not even in the language you prefer.
I've split your post into a separate topic.
Have a read of Pi-hole's Router setup assistance for FritzBox routers for possible configuration options.