You can delete, search or create gmail contacts very easily inside gmail user interface. Moreover, you can use this add on anywhere anytime in your gmail mobile applications. For Google Calendar, you can insert attendee, their address and phone into google calendar current event
If you want to use the Iphone or Ipad mobile application, please download via this link If you want to use the Iphone or Ipad mobile application, please download via this link https://apps.apple.com/us/app/contact-app-for-gmail/id1611022478
Features:
+ Add, update, delete contact
+ Manage contact 
+ Manage social network IDs such as facebook, twitter, linkedin
+ Support custom, dynamic fields. For example, you can add Skype custom field for a specific contact.
+ Search contact via email, phone, birthday,...
+ You can manage the following contact's information: first name, last name, birthday, phone, email, work and home address, prefix, company, job, note, ...
+ Search and add contact as an attendee of a google calendar event
+ Add contact phone and address to calendar event
+ Support more than 10 languages
How to use addon in Iphone, iPad,Android phone and tablets:
+ Install addon via gmail in web browser 
+ Install mobile gmail application
+ Open an email
+ Swipe to the bottom and click on G Contact Manager icon and enjoy

It sync across all devices. Your contacts will be synchronized to Android contacts in your Android phones after some seconds or a minute. You should turn on Wifi or 3G 4G network on your mobile phone to sync contacts and you will see your changes in the Contact app. For Iphone or iPad, you should synchronize Gmail Contacts information to your iCloud so you can see the changes.
We use some scopes, you can see why we use these scopes at this link https://www.2hac.com/contact-manager-privacy-policy/index.html
Resources and Tutorials
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➩ YouTube video tutorial: 
YouTube video tutorial: https://www.youtube.com/watch?v=pxMUdFkS7kI&list=PLk31adfFOxDGim3TDelc3yUOxLN2MrIho
Help: https://www.2hac.com/help/index.html
Email Support: 2hacstudio@gmail.com