Pi-Hole is acting weirdly

Not anymore :sweat_smile:

I re-enabled dhcp on the router and set the range to
All the devices that are not working (on an interval of 10 to 15min)have an ip address set on the address range (so the addresses given by the dhcp of pihole) and all the devices that are working have an ip address set on the address range
If I disable the DHCP server of my router, all the devices lose access to the internet on an interval of 10 to 15min

Yup, my mistake

These are the DNS addresses that I can't change. My router don't allow it that's why Im enabling dhcp on pi-hole
according to this : What can I do if I can't change manually set the DNS server on my router?

I can't directly with this router. That's why I disabled ipv6 completely in the router settings and now it uses ipv4 dns address (but I'm not sure).