Robots use advice-form, even with captcha

-- url of the page with the problem -- : hollandopleidingengroep.nl
-- HikaShop version -- : 4.4.2
-- Joomla version -- : 3.9.26
-- PHP version -- : 7.3.28
-- Browser(s) name and version -- : all browsers
-- Error-message(debug-mod must be tuned on) -- : no error

Hi there,

On my website we get many advice-requests for a product every day, that have been sends by a robot. There is a reCaptcha on the form, but still we get many of such emails.
Is there a direct url that robots can use to send these e-mails to overrule the captcha? And what is your advice to stop these spam?

Best regards,
Peter

Thank you for this very complete answer, even if this is beyond the scope of the great software you deliver.
I will check the solutions you mention, and try to accept the fact that spam will never be banned 100%.

Regards,
Peter