Gamingmate92
Have you tried setting DoT dns on your Fritz Box?
Go to DNS settings, scroll down to DoT dns and activate it with these settings:
( copy & paste dns11.quad9.net - this is the server with ECS support enabled)
If you want, you can also add custom, quad9's non TLS DNS servers as follows:
IPv4 primary 9.9.9.11 - IPv4 secondary 149.112.112.11
IPv6 primary 2620:fe::11 - IPv6 secondary 2620:fe::fe:11
I do not guarantee this solution will solve your slow downloads (i don't have these problems btw, and i'm with Aruba too), but at least you'll get encrypted DNS queries.