Is there anyway where we can use if/else concept in feature file? For example:
Scenario: User should be able to check login page
Given I am on login pag
No you can't and you shouldn't. Feature files are for business behaviour, not programming.
From your scenario I think you are trying to deal with different behaviour, depending on whether you are registered or not. To do this you would write two scenarios
Given I am registered
When I
Then I should ....
Given I am a new user
When I ...
Then I should be asked to register
Notice how these scenarios don't describe 'how' anything is done. Anything like `I click on foo' in feature is a smell and should be avoided.