Do you agree or disagree with the following statement? Private cars should be limited in the center area of big cities. You would use past personal experience to support your response.

20 in 30

The example is too long. Need two reasons. Try this pattern for Q1-Q2:

first 1-2 sentences: introduction. my opinion: A or B. agree or disagree. about 5-10 seconds

First, reason 1 (1 sentence) + why reason 1 (some arguments. 1-2 sentence) + a small conclusion for reason 1(like advantages of reason 1 or comparisons if not reason 1, 1-2 sentence). // about 15 seconds

Second, reason 2 (1 sentence) + why reason 2 (some arguments. 1-2 sentence) + a small conclusion for reason 2(like advantages of reason 2 or comparisons if not reason 2, 1-2 sentence). // about 15 seconds

Conclusion: Don't need a conclusion. (you can have one only when you don't have something to talk about)
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An example (Eating at home or restaurant) for First:
First,reason 1 (1 sentence: Eating at home can save money) + why reason 1(some arguments. 1-2 sentences: I can prepare cheaper food from food market; I don't need to drive or take a bus to reach the restaurant;) + small conclusions ( 1-2 sentences: with the money I saved, I can buy a good book to read; I can use the money for a trip...).