1. An overproduction of a particular product means that the cell is allocating energy and resources to produce what is not necessary, or what might even be toxic in higher quantities, at the cost of producing other substances that may be more vital for the cell’s survival.

2. Most likely this is the result of a positive feedback mechanism, because if it was negative feedback, the production of the substance would most likely cease when it reaches high concentrations (e.g. d[A]/dt = -k [A]). A positive feedback mechanism, however, requires a brake, which, in this scenario, may not have been present, thus leading to the overproduction of the substance.

3. I am not sure exactly what is meant by correcting the problem, but I believe all of the following are possible:
a) To decrease the production of the product, you can inhibit the enzyme that produces it, or turn off the gene that encodes the substance or the producing enzyme (in biotechnology this is achieved through knockout or RNA interference).
b) To decrease the activity of the product, you can use an enzyme inhibitor.
c) To increase the degradation of the product, you can tag it with ubiquitin using ubiquitin ligase.