Many 'groan ups' don't understand either and that is their fault.
In Australia Bibles are plentiful – but are not read enough. Those people are not interested enough to read it all and that is very sad. Australia today is being called a 'Post-Christian' country because so many are not serious Christians. In a census, 80% say they believe in God. But a great majority do not go further with it.
To your question: Jesus came to earth once, lived as a normal human. Preached for three years, speaking to thousands of people; in the fields, by Lake Galilee and wherever crowds were – and He taught, counselled and encouraged the twelve Disciples privately and so on for His three years on earth teaching them all He could about God and His kingdom. Then He was crucified once and for all – to pay for our sins then rose to life on the third day as He said He would!
No other person has ever done that!
Much about what Jesus did was in 300 prophecies spread over a thousand years. Jesus himself prophesied His Second Coming.
So, much of God's long-term plans have been fulfilled.
But the Second Coming is yet to happen.
Jesus will come again but as the ruler of the new earth He has promised to make.