What is good? Thoughts of a 16 year old PART 1

Hey Steemians!
I am going to introduce you to a series I'm going to start making on philosophy and ethics as this a a very interesting topic for me.

Helping people in need? Saving lives? Killing people? Lying?
What's the difference?

The answer: Nothing.

You guys might ask what this bold claim is all about.
In our world there are many actions and decision a human can make but who are we to decide what is good and what is bad?
Well obviously there are human rights and also killing people is against the law so it must be bad right?
WRONG
In this example it is just our society, our values and our common sense which say: 'Obviously it is bad to kill people!'
Let's conduct a little thought experiment:
We are living in a parallel universe and in this universe it is regarded as very GOOD to kill people.
People do it all the time and to be a good person you have to kill someone.

Now how can we decide whose ethical standpoint is correct? Our view or the view of this nasty other universe?

We can't.

This is the idea of moral relativism. We can never be 100% sure if anything is correct including our values.
Maybe killing someone is after all the best action to take because there is giant teddybear up in the sky who says:
All people who murder someone or get murdered will go to literal heaven.

Despite the chances of this probably being very low it is impossible for us to exclude this possibility and this is the point of moral relativism.

We claim to be so sure about what is good and what is bad even though we are barely in a position to make that decision.

This is my first post of series I am planning to make, titled 'What is good?'
I appreciate any kind of feedback and I am open to discussion in the comments.

Do YOU agree with this idea or do YOU have a different point to make?
Let me know!