Wi-Fi Connection weak

There are a number of ways to fix this.  What's best depends on how much you're willing to spend and how much work you're willing to do.  The latter is heavily dependent on how easy or difficult it is to run cables to the upstairs.

The most common way of dealing with this is to buy one of those mesh WiFi systems with multiple repeaters.  It's similar to getting more extenders, but you get an integrated system that tends to work a bit better than multiple extenders.

The better way to to cover a larger home is with wired WiFi access points.  There's only so much wireless bandwidth available, and a bunch of WiFi repeaters use up bandwidth with every repeat.  You don't need to buy commercial access points, though you certainly can if you want to.  They're not much more expensive than consumer grade gear, just more complicated to configure since they have more features.  Most WiFi routers and range extenders have an access point mode that will work with a wired connection back to the router.  Many mesh kits support a wired backhaul as well.

You may not need to put anything upstairs unless you want max speed upstairs.  WiFi goes through floors ok, especially if they're just the wooden floors in a typical house.  What you need to do really depends on how fast you want WiFi to be in a given spot.

Adding another option that a *MoCA* system may also be a solution for you. You can Google MoCA for more details / info.

@user_426098 I show one of xfinity expert has given out some great advice , this link https://comca.st/3Pet3wW also has some great information on trouble shooting your wifi connection