Active job

Slow internet connection could be due to internal wiring ?

I've been experiencing terrible internet service for over 6 months now and recently changed provider as well but its not resolved. I think internal wiring could also affect fixed line broadband service and just wanted to get this checked and possibly resolved or eliminated as a cause. Please help! P.S I do have VDSL connection at the moment but that had been the case since 2017 and only recently started giving me grief. I am also waiting for fibre connection but would like to have current wifi sorted until that happens.