Permissable cases of backbiting (e.g seeking marriage)

There seems to be confusion when backbiting is allowed.

Please let us remove this ignorance from ourselves

https://abdurrahman.org/2015/04/16/what-type-of-backbiting-is-permissible-imaam-an-nawawee/

Snippet

"If your objective can be achieved by simply saying: “It is not good for you to engage with him in business transactions” or “in a relationship through marriage” or by saying: “You should not do this” or anything similar to that, then adding more to this, such as by mentioning his bad characteristics is not permissible. And if the objective cannot be reached, except by specifically explaining that person’s condition to him, then you may mention that to him in detail."