@Riley_S Thank you again for your attention. Knowing that due to the TVs I will have to use my modem router, I will connect everything I can on cable (and get the 600MB speed) and stay with the 450...

Another detail, my switches are from tp-link: TP-Link TL-SG108 .

Dear @Riley_S Thank you for your attention, Yes, my modem is acting as a router, and I can't set it as bridge because my TV and telephone are provided by this modem (the signal receivers of the TVs...

Dear, Since I installed my new internet, a fiber point with a speed of 600 down/300 MB up, I haven't been able to reach the contracted speed using the deco m5 anymore (before I used a fiber 300/150)....