Upvote:4
Most people in France have multiple given names. I have three.
I don’t think I’ve ever provided anything but my “usual” given name (which, like for many people, happens to be the first one).
It may be a bit more difficult if your “usual” given name is not the first one, or even not one of your “official” given names. Some passports used to allow for that (french passports used to have the usual given name underlined, but I believe they stopped doing that a decade or two ago).
But in your case, giving just the first of your given names, nobody will care or even notice.
Upvote:6
No, it's not an issue. Second/middle names are typically ignored for airline tickets.
You do, however, need to make sure the name you enter matches your passport exactly for any visa/ETA applications.