Open the Contacts app on your phone
Tap Settings or Manage contacts
Select Sync contacts or Accounts
Choose your Google account
Turn on Contact sync
Open your phone’s Settings app
Tap Accounts or Passwords & accounts
Select Google
Choose your Gmail account
Enable Sync Contacts
Make sure Contacts permission is allowed for Google Contacts
Open the Google Contacts app
Sign in with your Gmail account
Turn on backup and sync if prompted
Check that contacts are saved to your Google account
Wait for the sync to complete
Verify contacts in contacts.google.com