search in SharePoint 2013 does not redirects to search center

Question

I have created a Site Collection based on Enterprise Search Center and changed search settings for all other site so that they use this search center, However I am facing two problems, 1. when I enter a search text in the input box on any page of my site it does not redirects to the search center. 2. It does not retrieve many results as when you enter same query text in the Search Center. (for example if I search for a profile it returns results when you search directly in Search Center but zero result in another site or site collection).