Let us see:
Open central administration.
Click Application management -> Open Manage Service Application.
Click Search Service Application.
In this page, click Query suggestions on the left side.
Click the Checkbox to enable showing of search suggestions.
Provide the language for the suggestion phrases ex: English, Arabic, Chinese etc.
In Always suggest phase -> click to import from the text file.
Before doing this, create a TXT file with some keyword suggestions.
Save the file.
Now, click Always suggest phase -> click to import from the text file.
Upload the document and click OK.
You can also restrict the suggested phrases, using never suggested phrases.
Click Save Settings.
Next, open Monitoring in central admin.
Under timer jobs -> Click Review job definitions.
Find the timer job -> Prepare the query suggestions.
Open it and run now, set the timer according to what kind of time interval is required to run this job, as per your scenario.
All set to go.
Now, open SharePoint site.
Now, type some queries in the search input box and you will get the result like:
This is the final result you get, like Google autocomplete.