Odroid N2 Nextcloud server uses to much bandwith

Dear Community,

I recently installed a Odroid N2 Nextcloud server at home but now some of the other devices in my home network are experiencing strong slowdowns in bandwith.

Now I would like to limit bandwith of all external nextcloud accesses (accesses through the internet) to 50 % of my available bandwith.
Network internal accesses to the nextcloud should stay fast.

I was thinking of Qos settings in my router maybe? or how would you solve this problem?

Many thanks in advance!

Note sure if there are possibilities to limit bandwidth webserver internally, but I guess solving this router side is the best way indeed.