Where can report a website bug?
Oo https://nextcloud.com/contribute/ there is a wrong link.
https://transifex.com/nextcloud > https://transifex.com/nextcloud/nextcloud/
You’re referring to Transifex links, what kind of problem have you identified, a translation problem? Otherwise the following repository might be better to address an issue: https://github.com/nextcloud/nextcloud.com/