WordPress has no captcha at all.
Which plugin are you using for this?
There is a CAPTCHA necessary for the login when I want to login to the editor website (www.vinca.at/wp/wp-login.php)
As I mentioned earlier, WordPress doesn’t come with any captcha at all.
The captcha on your login page is from the “SI CAPTCHA Anti-Spam” plugin.
This plugin has been permanently closed since 2018, and thus not seen any updates since this time (and never going to see any updates going forward): https://wordpress.org/plugins/si-captcha-for-wordpress/
You need to completely remove this plugin from your site.
Use FTP or the web-based File Manager from your hosting provider’s control panel to access your WordPress site’s files. Navigate to /wp/wp-content/plugins/ and rename (or just delete) the folder si-captcha-for-wordpress to completely remove the problematic plugin from your site.
Good luck!