in short you need to post to the login page
https://auth.marktplaats.nl/accounts/authentication/login
with username and password (field for username bieng j_username, and password bieng password)
you will need cookies set:
curl_setopt($ch,CURLOPT_COOKIEJAR,$cookieFile);
curl_setopt($ch,CURLOPT_COOKIEFILE,$cookieFile);
verify cookieFile exists and is writeable.
you may need to disable https verification (or enable it properly)
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
you may also need to set browser type (if the site uses it for sending diffirent content or something)
that should get you logged in, then just check the urls, forms that you want to use and send the same data you would manually.