Corrections in red.

Suggestions in blue.

Explanations in green, as necessary. 

I love my country, my planet, and my universe

I am 20 years old and come from Indonesia, a one of the beautiful country. I am majoring in My subject in my college is Geophysics in college. I hope to become wish I can be a great geophysicist after I i graduate. What do I i learn about? Earth. Yes, I learn about many things in our Earth. That's why I love my subject. I hope I can solve every problems in our planet has. I will do what I can do to save our Earth and I hope you, too (The "too" here is not wholly necessary; I would consider taking it out). I want to bring peace to Make our Earth in peace and do whatever I can (this has a slightly different meaning but is much more natural) the the best action for our environment. It just takes a little good action ("little good action" is a little awkward, perhaps use "one small action") and trust me, you'll get an amazing rewards that comes from your heart and allows can give you to see the postive impact the same impacts of what you did.