This is the problem with coming to a show with expectations, if they don't meet it, you're disappointed.

At least based on the synopsis, it gave me a sense that the ML will be switching between two worlds and solve his cases because of the knowledge he gains going back and forth.

Unfortunately, that's not what happened. It was a one-time major switch, and then that was it. When he returned, he rarely used his knowledge from the other world to solve cases in his own world. Everything simply diverged, that he had to investigate from the bottom up.

The other world? You'll see it again in the ending as sort of closure only, but did not answer questions it left.