Not used or heard of them but I'd say that simply using Chrono24 should not be seen as any kind of recommendation at all. There are good and bad sellers on C24.
You're doing the right thing to check up on the company.
P.S. I just looked at their website and found the following:-
(1) The website appears not to adhere to UK and EU legal requirements for provision of company contact or registration information. E.g. No company or business registration numbers, no VAT number, no proprietor's name(s), no registered address, not even a trading address.
(2) The website contact form just has a mobile number as a UK contact number (in addition to the French phone number and the email address).
(3) On the website 'About us' page they claim to "have over eight points of sales all around the world and one shop" but none of them is actually listed as far as I can see.
(4) Their domain name is registered using a privacy service so one cannot see who the proprietor is.
In short, I would not use this company unless I knew them very well by other means. They may well be genuine but, as things stand, you do not know whom you are actually dealing with.