Hello everyone

I have an ax73.
My service provider gives me 1000 mb/s internet, of which 300 mb/s is guaranteed.
I found that my router is only capable of a maximum of 90 mb/s.
Last time I reset it to factory settings. Then it had 800 mb/s for 2 weeks, then 2 weeks later only 300 mb/s. Then again only 90 mb/s.
I just reset it to factory settings, now it's still stable at only 90 mb/s.
I have already tried everything, but unfortunately there is no solution. The support does not respond to my email.