I am not sure I can solve all your WiFi problems, but I can tell you how I solved mine.
I used to have a DSL modem connected to a Netgear router. It was attached to my main computer located in the kitchen. The system worked but it never worked well. The bedrooms are at the opposite end of the house and had only a weak WiFi signal. Outside stucco walls also hindered the WiFi signal. Many times I had a stronger signal from my neighbor’s WiFi than from mine.
Everything has changed now. I purchased the $499 eero Home WiFi System from Amazon. The system consists of three routers that may be placed anywhere in the house. They link together to give complete coverage. One for the kitchen, one for the family room, and one for the bedroom. Installation was simple. These routers connect directly to your smart phone, and you do the setup right there on the phone. The process was painless, and it worked. I only wish I had installed the system earlier.