When do you know if your friend is a true/genuine friend?

What the title basically says :) I have AuDHD sometimes struggles with reading social cues for myself but have no issues reading them for other people, I’m currently 20 F at uni studying and currently experiencing a loss of a friend with no closure.

No matter how much I change my behaviour/reflect on my past friendships so I can do better and be a better version of myself.

With any new friendships I make recently, I always seem to attract the same kind of friendship even when I don’t mean it. And now I’m getting to the point of being frustrated and confused and feel like I’m always the problem despite my family and partner telling me otherwise.