I think I bought a fake. What now?
In short: Keep the card, the packaging and the listing, and do not alter anything. An authentication opinion with photographs gives you something concrete to show the seller or the platform, which decide for themselves what weight to give it.
Save screenshots of the listing and the messages before they disappear, and note the dates. Then get an opinion: the sheet names each check and shows the photographs, which is far more useful in a dispute than "it looks wrong to me".
I do not negotiate with the seller or the platform for you. You can share the opinion wherever it helps, and the record behind it is kept under the retention and consent policy.