try to make a Firmware Reflesh, maybe it could be slightly corrupted, sometimes nothing strange can happen! Obviously it is an attempt, I cannot guarantee you that this is actually the case, but from something you have to start.

@PasKy 

try to make a Firmware Reflesh, maybe it could be slightly corrupted

i think it is corrupted, i tried to downgrade the firmware, and tried to reinstall the same version both ways aren't working i always et internal error 01 in the process after uploading the bin file. If "reflesh" is something else I'll  be glad to know what is it. 
Now it has been three days I'm starting to lose hope on my d9 🙁

... by any chance the problem arises after changing some parameter that was not active before? because the problem that arises is quite strange ... it almost makes me think (the doubt is seen that apart from the error everything works!) that obsolescence has been programmed ... but let's wait for the technician, maybe he will know how to solve the problem ... even if I have strong doubts ... since now Tp-Link tends only to make numbers and not really worry about consumers!

@PasKy 

I didn't change anything, i didn't touch the router or its UI for 6 months i live alone and it was working continuously good until three days ago i thought that maybe any router needs a rest from time to time so i decided to turn it off overnight, next day morning the problem occurred when i turned it on, now all is working except the DSL led that stays off like it doesn't recognize the phone line anymore.
Now the wireless network is up and running with no internet, everything i try to do now in the UI i get inernal error msg even when i try to switch tabs or navigate between settings every click is followed by internal error code "1" and sometimes "9003" and the UI is very slow than normally.

As i mentioned in the first post, the same problem happened with the same router once before, but it was briefly gone by itself. It can't be a faulty hardware because of the UI behavior i think it's a firmware problem since the router is still like new. I tried different functions of the D9, USB Sharing/FTP Server/Media Server/Printer Server all works fine except the xDSL !!!!!! Any help from tech team plzzz

... se utilizzi il protocollo Annex A/L/M prova questa versione più recente di quella installata sulla tua!                                                       

  https://www.tp-link.com/it/support/download/archer-d9/#Firmware