First, nearly all problems are going to be solved by forcing moves (checks, captures, threats) on the first move. Occasionally, you run across more subtle problems where the first move is a quiet move but those are often zugzwangs and they aren't that common.
Second, It's good to look at the weaknesses in the position especially hanging pieces ie "that ...
for example this one below,don't even know where to begin.Earlier the
way I solved problems was finding all the checks,captures and threats
and the solution used to come within few seconds but now things are
not that easy
"Finding all the checks,captures and threats" looks like a great way to solve the puzzle you've posted. There are no immediate ...