how to sync webmail contacts with K-9 mail app

How can I my sync webmail contacts with the K-9 mail app on my Android?

You can sync contacts from webmail to nextcloud and then to your phone:
https://howto.disroot.org/en/nextcloud/apps/webmail
https://howto.disroot.org/en/nextcloud/sync-with-your-cloud/android/calendars-contacts-and-tasks

Thanks a lot. I’ll try the instructions at those links and let you know how it goes.