but everytime after a block took too longer to be mined then the upcoming 2 or more blocks will be mined in next few minutes
Time taken for a block to me mined does not affect the time for the next block which is in line. It's not a case where if a block takes too long before being confirmed the next one will take a short time, it's just about how fast miners can solve the puzzle.
Only at the point if difficulty adjustments can the time taken for block confirmation be adjusted.