There really are no right or wrong answers to this type of question, so I will say that the assumptions you based your response on are pretty good.
I think the fatal flaw here is that the author assumes an understanding of the properties of metals is necessary to solve the purchasing problem, which will in turn solve the problem of falling revenue's. You touched on that, so you're on the right track.
A few pieces of advice:
Do not bother repeating the main point of the argument back to the reader - it is not necessary. You can just reference the text rather than saying "the author of the report concludes..." and basically rewrite what we already know.
In your second paragraph, you started to discuss a reason for the loss of revenue - but you didn't develop the idea properly. You need to work through it more, so that I understand what you mean. How does the competition dampen the price of the product? And how does this lead to a loss of market share? You need to be clear on your reasoning, the point you made was disjointed and incomplete.
In your third paragraph, I think you made an error in reasoning. You ended by stating that the background of the person in question is what makes them a good planner. Unfortunately, this doesn't really fit well with your argument, and you didn't develop the idea to make it fit. You need to expand on that thought and help me understand how it relates. My guess is that you want to say the person in question is a good planner, and that it is an unfair assumption to suggest he is not - so why not clearly state that?
Lastly, there are some grammar errors, but unfortunately I don't have the time to comb through them. You should continue to work on your grammar.