Some translations set quotations from the Old Testament farther to the right on the page than the rest of the text. The ULB does this with the quoted material in verse 3.
Fruit is a common picture word in the scriptures. Writers use it to describe the results of either good or bad behavior. In this chapter, good fruit is the result of living as God commands. (See: [[rc://en/tw/dict/bible/other/fruit]])
No one knows for sure whether the "kingdom of heaven" was present or still coming when John spoke these words. English translations often use the phrase "at hand," but these words can be difficult to translate. Other versions use the phrases "is coming near" and "has come near."