Answers to the Rows and Pieces can be determined as follows:
The solver will note that several of the rows are too long to fit in the grid. Entries in those rows all have numbers in their answers, some split between words (leFOU/Rosy). Replacing those entries with the actual number will allow the entries to fit in the grid. However, the puzzle pieces are all the right size and have no such numbers to reduce to fit in their respective shapes. So the grid fills out two different ways:
The next step is to note that the letters in all of the numbered boxes, reading top‐to‐bottom and left‐to‐right, spell "SHAKASHAKA". A google search will reveal that this is a logic puzzle type consisting of a bare grid combined with some number of black squares that can have numbers in them. Using only the numbered boxes in the solved puzzle gives this grid:
Following Shakashaka rules, this puzzle gives a unique solution that includes 28 full squares (indicated in green):
Going back to the solved puzzle grid, those green squares spell out the message "PREDICTING BY PROJECTING TRENDS". The answer to the puzzle is EXTRAPOLATING.