I'm assuming that the "Plastic bags" at the top is a title, in which case it should be more clearly marked to be so – Here I'd advise at least capitals on both words and a space between it and the article.
"Astounding" on its own doesn't work, you either have to say "[It's] Astounding! Plastic bags aren't free...", but that's not the atmosphere you want to give, I think. Or you must make it into an adverb: "Astoundingly". "Cleans" is a verb, not an adjective, which would be "clean", and saying "the universe" makes little sense. Say "the environment" instead.
"The rule applies in" does make sense, but it is slightly counter-intuitive. We may need a teacher for that one.
And your final sentence is the least sensical of the lot. You don't say you were wonderful in this situation and "I got the point" is a little random here.
All in all, needs a lot of tweaking.
[Not a teacher]
Student or Learner