@macite What you’ve done so far isn’t correct and is insufficient for Netlify to verify.
The relevant Support Guide is here:
https://answers.netlify.com/t/support-guide-another-site-is-using-this-domain-verifying-domain-ownership-for-netlify-production-domain/13765
The name should be verified-for-netlify
The value should be:
https://answers.netlify.com/t/setup-custom-domain-transfer-from-other-team/127882
You’ve currently added:
And:
The second one might be enough, since it’s at least unique to you.