Luckily Bing is really easy to disable, and you’ll just need to get to the Cortana search settings screen — the easiest way to do this is to type “cortana settings” into the Start Menu and choose the “Cortana & Search settings” item.
This will bring up the settings dialog, which is going to look different depending on whether you’ve already disabled Cortana or not.
If you want to disable the Bing integration, you’re going to also have to disable Cortana — so flip that switch to Off.
Now that you’ve disabled Cortana, the rest of the dialog will change and you’ll see an option for “Search online and include web results”, which you are going to want to disable as well — this is how you actually disable Bing from the Start Menu.
And now when you search for anything, it’s going to only search your own PC.