Depending upon the need, mode or desire, you may need to sort all the contacts in your phone book to be sorted by the first name. It may make you convenient if you are searching some contacts who are saved by first name only.
We must remember that in Western culture, a person is called and her/his name is saved by last name. But if you are from the east, you may feel perplexed by the last name culture.
Anyhow, if you feel need to sort the contacts in your phone book to be sorted by first name, you may do so, easily. But, if you need help to do so, just see the instructions.
Instructions
1: Tap the icon of the ‘Phone Dialer’ app at the Home screen of your Android 5.1 Lollipop device to open up the ‘Phone Dialer’ app screen.
2: At the ‘Phone Dialer’ app screen, tap the settings button, placed at the top right corner of the screen. It will open up a popup menu.
3: Tap ‘Settings’ in the popup menu.
4: At the ‘Settings’ screen, tap the ‘General’.
5: At the ‘General’ screen, see the current status of the ‘Sort by’, under the ‘Contact display options’ section is set to ‘Last name’. It mean, currently, contacts are sorted by the last name. 
6: If you want to change the current setting, tap the ‘Sort by – Last name’. It will open up a prompt where it is, currently, sorted by with current selection of ‘Last name’.
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