the difficulties you faced in the fediverse

Some networks are a bit confusing, like Misskey and Firefish. On Lemmy sometimes things don't federate as you'd expect them, like Mastodon <-> Lemmy. Even between different Lemmy instances sometimes things don't federate, so people on different instances will see different things on the same post. Not hard to get used to, overall, but it's there.

challenges faced by the fediverse in attracting users and retain them

I'm not really inside that part of the fediverse. I enjoy Lemmy, and check Mastodon ocasionally. I guess an issue is that the people I follow on centralized social media aren't really on fediverse. Also, I think videos are a big issue. Video-based content is huge on the internet, but the fediverse video-sharing platforms just aren't very good.

your experience in fediverse

I've been having tons of fun. Lots of fun conversations and interesting topics to explore. Definitely positive.

feedbacks about fediverse

As I mentioned before I think video-based stuff really needs to improve. Some connectivity/federation issues also need to be ironed out. I also think chatroom style social-media would be great on the fediverse. Lemmy does that a little bit with the Chat comments, but it's not the same thing. I'm thinking something like Discord. Matrix can be federated I think, it does run AP, but it's not in practice AFAIK.

your suggestions to improve fediverse

Basically what I said above: focus on video content more and effective chatrooms.

setbacks of fediverse and anything related to fediverse.

Not sure what this means? Setbacks? I guess dumbasses talking shit online is an issue? A lot of people hear "fediverse, activitypub, blah blah blah" and decide it's "not for them". I guess it's hard to make people see the value of decentralized social media. And it's definitely difficult to make people let go of their virtual lives on other social media for something that's still a bit buggy and not used by a lot of people. Well there's a lot of people on the fediverse but a lot (A LOT) less than on other social media platforms.