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Ezzat, I agrre with the native speaker who corrected your sentence. When something had already happened at a time in the past, we use "Past Perfect Tense" For example, Event 1: Jack finished his job at 14:45 Evernt 2: The boss came to the office at 15:00 ->Jack had finished his job when the boss came to office at 15:00. Let's see another example. Event 1: Jack left the car at 7:55 Event 2: Jack's car exploded at 8:00 -> Jack had left the car when his car exploded. We can know by "past perfect tense" that event 1 happened earlier than event 2. Your sentence: "I had noticed that the road became narrower" is semantically wrong, because you will never notice something that has not happened. In sum, "I noticed that the road became narrower." is correct.

Depending on the context, there was nothing wrong with your sentence, but without seeing the context I can't be sure. Your sentence was correct if you intended to say that you noticed this before some particular point in time, or before something else happened. So, for example, you might be saying something like "Before it began raining, I had noticed that the road became narrower." But if you are just saying that you noticed it, and you are not saying anything about when you noticed it, then the correction is correct.