Hello Gabor Nemes,

I hope you are doing well.

You can try this Step:

1. On your Android device, open the “Settings” app.

2. The name of this option may vary depending on your device and Android version.

3. If you have multiple accounts, select the Google account you want to disable contact sync for.

4. This may be located under the "Account settings" or "Sync settings" section.

5. Look for "Contacts" or "People details" and turn off the sync toggle switch. This will disable the synchronization of your contacts with your Google account.

6. You may be prompted to confirm that you want to stop syncing contacts. Confirm your choice.

7. You can also review and customize contact sync settings within your Google account. 

I hope this will help you.

Thanks & Regards,
Email:    odoo@aktivsoftware.com     

Skype: kalpeshmaheshwari