Well, the Gangsta manga ends with a mix of closure and ambiguity. Some characters get the resolutions they deserve, but there are still elements that make you think and wonder about the future.
No. The original Spongebob series is all about fun, friendship and adventures in Bikini Bottom. The 'Spongebob real story' is a completely different and often very dark and inappropriate take that has nothing to do with the original positive nature of the show.
It could mean that there is a fan - created story (fanfic) about Naruto where the characters are depicted in a 'gangsta' - like style. For example, they might have the attitude, appearance, or behavior associated with gangsters in a modern or unique setting within the Naruto universe.
Probably not as popular as the more traditional Naruto fanfics. The Naruto series has a large following for its original ninja - based story, and the 'gangsta' theme might be a bit too far - fetched for some fans.