Override Buttons
Step 1. Go to Object Manager, enter text Opportunity in the search bar, and click Opportunity.
Step 2. Opportunity Object Manager opens, go to Buttons, Links, and Actions and scroll down to select New against Edit.
Step 3.1. Choose No override (use default) against Salesforce Classic Override.
Step 3.2. Choose Use the Salesforce Classic override against Mobile Override.
Step 3.3. Click Save.
Step 4. Similarly, perform all the actions as listed under step 3 above and change the page for the Edit button.
Pages are overridden to Standard page for the New and Edit buttons against Mobile Override for the Opportunity object.
Clone Lightning Page
Step 5. In Opportunity Object Manager opens, go to Lightning Record Pages and click to open the Lightning Record Page that is currently assigned as your Desktop Org Default.
Step 6. Click Clone.
Step 7. Lightning App Builder opens, go to the Details tab and click the delete icon of the component on this tab.
Step 8. Drag & drop Record Detail component onto the Details tab.
Step 9. Click Save.
Step 10. Click Activate.
Step 11. Click Assign as Org Default.
Step 12. Choose Phone and click Next.
Step 13. Click Save.
Step 14. Go back to Lightning Record Pages in Opportunity Object Manager and note that there are now two separate pages that are assigned as Phone and Desktop Org Defaults, respectively.
Opportunity Standard page can now be accessed from your mobile devices.