You need to play through many, many master level tournament games to see what they do next in positions that result from your basic opening setups.
What do I do when I can't do anything in chess?

You might appreciate Michael Stean book "Simple Chess". The last chapter on Space comes to mind where he just says something like "Just try and control more space and not worry about what comes next..."

You might appreciate Michael Stean book "Simple Chess". The last chapter on Space comes to mind where he just says something like "Just try and control more space and not worry about what comes next..."
Ziggy nails it. Silman's How to Reassess Your Chess is also helpful. So is Peter Romanovsky, Chess Middlegame Planning. So is Kotov and Keres, The Art of the Middlegame.
I also think that playing through hundreds of master games quickly will give you a feel for typical middlegame plans.
n long tournament games, I usually begin with a standard opening depending on what the opponent does.
Then when we reach the middle game, I can't figure out what I should do. I don't know where to attack, my pieces are in the best position they can be and maneuvering over all to one spot will take lots of time. The opponent has a solid foritfication that I can't see how I can break through, even though my pieces are all controlling/contesting the center.
However, this problem does not arive in blitz. There's bound to be mistakes for either me to take advantage of or for me to attempt to correct, but this never happens in standard chess.