You can back up your contacts to your internal storage or Google account.
1. Go to Contacts, then tap the Circle with a letter or your profile picture menu icon at the top right of the screen.
2. Contacts app Settings > Export.
Then, do one of the following:
To export contacts to the internal storage:
Tap Export to .vcf file. Select the location where to save the contacts and tap SAVE.
To export contacts to your Google account:
Ensure you are logged into your account.
Go to Settings > Users & accounts > tap the desired Google account > Account sync > ensure Contacts is toggled on.
Note: Contacts will be updated during the next synchronization.
To force an immediate synchronization with Google:
Go to Settings > Users & accounts > tap the desired Google account > Account sync > tap the 3 vertical dots > tap Sync now.