Introduction is effectively paraphrased but does NOT NEED to be restructured or written differently.
Overview shows at least 2 key trends.
Overview must state key trends of ALL drawings. Many candidates write "Company A has the highest sales in 2000" in an image that includes Company B, C, D, and the period from 1990 to 2000 - this is NOT considered a key trend.
In the body paragraph, it is best to compare both horizontally and vertically. For example, you should both rate [A] as increasing, but also comment [A] as the highest. However, this is a difficult skill which requires observation, good logic and a certain level of language.
To gain a. band 7 there must be any grammatical errors, or only limited grammatical errors (2% of text through mistakes, not ignorance).
Diversify the vocabulary used to describe trends: increasing/decreasing, strong/mild and related words. E.g "upswing", "negligible". You don't have to bombard the task with 100 difficult words, but at least 2-4 difficult words.
Use a variety of words that are relevant to the topic. Besides common words such as increase-decrease, diversifying vocabulary by topics provided is also a bright spot. For example - if the topic is about population, try to use words such as "demographics", "single-person households" etc.
Link paragraphs coherently without drawing attention. Avoid using obvious words such as firstly, secondly, regarding, in terms of… However, bear in mind that it is very difficult to keep the coherence without using many conjunctions (otherwise it will fall to band 5 because of lack of linkage).