What are most common concepts that Allah tell us in Quran?

Salam, I had a currious question from a non-muslim friend, and I do not have enough knowledge to answer.. The question was : When we read and understand Quran (fully), what are the most common concepts, messages, or in another words, if to make percentage of most important things in Quran, what would be those things ? Exemaple : 30% of Quran is focused in "what is allowed to eat/drink", 10% is relationship with parents, 20% rules to follow for mariage.. I really hope that my question will not be misunderstood and will not offence anyone.