Thankyou for your question, one which has caused anxiety for Christians from the earliest times.

In Paul’s first letter to the Thessalonians, they were anxious because they thought that those who had died before the return of Jesus might be lost forever (1 Thessalonians 4:13-18). This indicates that they surely thought Jesus would return soon, within their lifetimes. Yet Jesus himself declared that only God the Father knew the time of his return and so the disciples were to be diligent as they didn’t know the time of his return (Mark 13:32-37).

The main part of the Bible I would direct you to look at however is 2 Peter chapter 3 where he declares that people will mock the belief that Jesus is returning (verse 4). Peter responds by pointing out that time does not operate for God as it does for us (verse 8), but his delay is due to his waiting for people to come to repentence (verse 9).

Ultimately, Christians today are in a similar position to the early church in so much as we do not know when he will return. However we can be confident that he will return because he promised that he would die, be raised, (Mark 10:32-34) return to Father and then return in glory (Acts 1:11). God has demonstrated in history that Jesus is real, and really died and rose from the dead (1 Corinthians 15:3-5) so we can trust that Jesus is real and will really return on that basis.

I hope that helps you.