Answer:
Step 1: Visit iCloud.com and log in with your Apple ID and password
At the same time, a window also pops up on iDevice
you need to click "Allow"
Copy the code from your phone to icloud.com
Step 2: Once signed in, select Settings on homepage
Step 3: Click "Manage" Apple ID.
Step 4: You will be directed to another site – appleid.apple.com
input your password to log in and verify it with Apple ID verification code.
Step 5: Then you will enter the manage page.
Click "Edit" in Security column.
Step 6: Click "Turn Off Two-Factor Authentication"
then confirm it.
Step 7: Then you need to select your security questions and answer them
click "Continue" after confirming your birthday and rescue email.
After all of these steps, you have turned off two factor authentication for Apple ID successfully.
Source : https://www.imobie.com/guide/anytrans/how-to-turn-off-two-step-verification-in-icloud.htm