Q: Dying wifi mac pro 2009 El Capitan

My ability to connect to the internet has slowly been fading for the past few weeks.

Now when I wake the computer the internet connection may be strong but quickly fades, then essentially stops.

Turning the wifi on and off (at the computer) sometimes brings the connection back briefly.

When logged in as a guest user the connection seems strong.

My Macbook pro and other devices on the same network have no problems with the internet connection or speed.

Any suggestions appreciated.