Hi Experts,

I am looking for some advice in replacing my own router/modem in house. 

In my current setup I have a NBN Connection with NBN Modem -which is connected to Technicolor TG789Vac  V2 HP (8 years old  )  - followed by a Deco M5 connecting into switch which is connected to 6 network ports around house. Wth main deco I have 2 other slave Deco M5 providing the wifi connectivity. 

I recently changed my plan to Utlta fast which has speed of over 5000 mpbs from 250/50.  Even after changing plan i was getting only approx 60-70 Mpbs . during troubleshooting i was told that it was my  Technicolour router which is the issue & restricting my speed. We tried connecting laptop directly via NBN Modem & we could see the difference.  I have two questions 

1) I read somewhere that i could replace the router with Deco M5 which has capability to handle that speed. I tried removing my router & connected main deco directly to NBN Modem.  For that I tried configuring the main Deco on PPPOE by changing teh configuration under internet settings from dynamic ip to PPPOE & providing the user name & password which was provided by nbn company. It didnt work at all & i had to change it back  to my original configuration.  Can i use Deco m5 as router by connecting it directly to NBN Modem , if yes,do i need to reset it completely to configure it again from scratch.  

2) Is Deco M5 compatible with TP-LINK AX3000 Dual Band Gigabit Wi-Fi 6 Router.  If i  replace my existing router Technicolor TG789Vac with TP-LINK AX3000, will i be able to still use as per my current setup ?

Many thanks in avdvance,

Ajay