>>606
まず、英語では同じ単語（car）を繰り返すのはよくない
あとsell their carsとするのはやや変で、sell carsでいいんじゃないかね
the car technologyのtheは不要、というか間違い

文字数稼ぎのためか、不要で不自然な繰り返しが多いが、不自然な部分に目をつぶって添削をすると、

I believe that the number of cars in cities should not be limited.
There are two reasons.
First, if the number of cars is limited, sales at automakers would plunge, damaging the broader economy.
In addition, technology has been improving of late, so cars utilizes gasoline more efficiently than ever.
Because of these reasons, the number of cars in cities should not be regulated.