Trying to understand the line between expressing hurt and backbiting

As-salamu alaykum everyone. I really try to avoid speaking ill of others and usually change the subject when conversations turn that way. But I have a question. When someone does something clearly wrong and with bad intentions, and I talk about what they did or what their motives might be-without attacking them as a person-is that considered backbiting (ghibah)? For instance, imagine someone knows two family members have a difficult relationship and then tells small lies to make things worse. If I see this and say something like, 'I don't think their intentions were good' or 'That was a deceitful thing to do, knowing the situation,' am I backbiting? What if I vent my frustration by saying, 'I don't understand why they would do something so hurtful and lack the basic decency not to tamper with family ties'? Also, what if I'm really upset by how lazy, thoughtless, or unkind someone is being toward me or another person, and I talk to a trusted friend about how their behavior is frustrating, but without cursing or insulting them? I personally dislike gossiping about people's lives for entertainment. I only talk about my own experiences, which sometimes involve things others have done. But what about discussing something that happened in another Muslim's life, not for fun, but because you're genuinely happy for their success or concerned for their hardship and want to share that with a close friend? Is that just idle gossip? Sorry for writing so much. I've been feeling uneasy about some things I've said and wanted clarity on this. May Allah (SWT) forgive us all, guide our intentions, and make our words and deeds pleasing to Him. Ameen. Jazakum Allahu khayran.