Home internet speeds extremely inconsistent and connection drops intermittently

I had excellent service with the TMobile home internet.  The moment I had troubles is when I switched my cell phones from Verizon to TMobile.  Turns out that we are de-prioritizing the Nokia gateway when our family is using magenta Max data on our phones.  I wasn't connecting the phones to the gateway to keep the load off of it and the phones had unlimited premium data.  Turns out all the devices in the house are sharing and fighting over the same bandwidth even if each individual device is on its own data.  It is causing so much issues.  I guess I should have kept Verizon phone services and just keep TMOBILE home internet only.  If you live close to someone using T-Mobile or Metro they will also be sharing your data.  My family lives next door and they are hurting our speeds as well when they use their metro phone (same tower as TMobile) to watch YouTube and want not.  They don't have home internet so they are always on their phones and they are close enough to our house that I know when they are watching YouTube.  Did some crazy testing to figure out our issue.