Browser keeping going via yahoo search even though google is set as home

Go to 'History' in the Safari menu bar and 'clear all history'. Then 'exit' safari from the menu bar again. Launch Safari now and see if that helps.

If you remember when this problem started, then think of what you did just before it started. If you installed some app, then that would most likely be the culprit.

It is caused by some extension you have installed. Remove the extension and reset the browser (clear all cookies, cache, temp files). You will have to sign in again, but that is okay.

Try in reverse chronological order. Remove the one that you installed most recently, and see if that helps. Then remove the one installed just before that, and so on.