Which Contacts app?

Go to settings, apps, Samsung contacts, and disable

 

I have read somewhere that you can't change the default contacts app on Samsung phones. Alternatively, you could change the default contact storage location. I'm currently not using a Samsung phone, but according to some other websites, you can set this in Contacts -> menu -> Manage contacts -> Default storage location -> choose Google.

 

It might take a time to sync the contacts with Google Contacts then. Do the newly added contacts show up after some time (e.g. 30 minutes) in Google Contacts? Also check if syncing is turned on for your Google account and contacts in the Settings app. See this webpage on how to enable auto sync: https://www.samsung.com/hk_en/support/mobile-devices/how-to-disable-enable-auto-sync/

 

Orange contacts = Samsung. Avoid.
Blue contacts - Google. Use.