Two-step verification is one of the best features to secure your WhatsApp account, WhatsApp will periodically ask you to enter your six digit pin, If you have forget your pin you will not be able to send or receive any messages until you reset this pin, there is no option to disable this without disabling the two-step verification feature. You can disable two-step verification by following below given steps:-
1 Disable Two-Step Verification Without Pin
If you have forget your six digit pin that you have created at the time of enabling two-step verification you can still deactivate the two step verification, for that you need to tap on forget pin.
2 Tap On Disable
You will be asked to disable two-step verification, click on disable and your two-step verification is disabled.
3 Disable Two-Step-Verification With Pin
If have the pin that you have created at the time of two step verification you can disable this feature for that first go to WhatsApp homepage then click on three dots given on top right corner.
4 Tap On Settings
After clicking on three dots you will get some operations to choose you have to click on settings.
5 Tap On Account
Now you will be directed on your profile setting page in which you have to tap on "Account" option given on top.
6 Select Two-Step Verification
Under account option you will find two-step verification option select this option and move forward. 
7 Tap On Disable
You will be asked to disable two-step verification, click on disable and your two-step verification is disabled.
8 Tap on Disable to Confirm
Now You will be asked to choose whether you want to disable the two-step verification or you want to cancel this operation click on disable button to confirm.
9 Here The Two-Step Verification Is Disabled.
