Will a signal booster improve my WiFi?

A cell phone signal booster will only improve your cellular signal. It will not improve your WiFi.

While a signal booster will significantly improve your cellular signal, it will not improve the WiFi for your home broadband Internet. Signal boosters are designed to only work on certain wireless frequencies that are used for cellular networks. WiFi uses different frequencies, so it is not affected by a signal booster.

If you're using a wireless hotspot (MiFi, Jetpack, etc.), then a signal booster will improve the data speeds that you'll be receiving from the device, but it will not be able to increase the size of the area where you're able to connect to the hotspot via WiFi.