To
make sure that your lead is directed to the landing page, please make
sure that you have specified the right URL in the Landing Page URL
section.
Go to Setup > Developer Space > Webforms.
Select the web form that you have created and click on Next Step.
Under Form Details, enter the desired URL to which you want to direct your lead on submitting the form.
Read more about setting up web forms
here.
Note: You have to use the newly generated code and host in your website to apply the recent changes you have made to your web form.