Give me useful suggestion, How to merge payment and shipping method steps in checkout.
- Create a new checkout step and for the sake of compatibility, upgradability and easy maintenance, do not edit the default Magento code, add your customizations in a separate module.
- Customize the view of the new step, show the required checkout ui components.
- Change the checkout flow.
This is no small task, start by reading here:
If you need a good example of modifying the checkout:
and the demo: https://demo.cleancheckout.com/
You can try any One step checkout for that below I have provided some links with paid and free extensions.
Onestep Checkout: https://www.onestepcheckout.com/magento-2/
Iwdagency: https://www.iwdagency.com/extensions/one-step-page-checkout.html (thay have free also)