18 years old

Today is my best friend's birthday!
I am completely (absolutely is ok, but completely is a better word for this sentence) happy because my friend became 18 years old.
18.. such a nice dream to be started. (No capital because this sentence starts with 18 not such. This is a difficult one to "correct" because it's such a creative use of language. I think "journey" would be better than dream.)
My friend and I would like to travel the beautiful countries, islands and places! (... and now I keep reading. In the last sentence, I meant "journey" in a metaphorical sence as in "Life is a journey, not a destination." Of course, now I read about our plans, it's even more appropriate.)
We are going to enter/go to/start/begin the  university to enjoy the a totally different lifestyle/way of life.
We are worried but excited! It is fanstatic!/.
Then, I hope that we can achieve success in life to help the most helpless people. (Don't forget your punctuation marks! They are important in English.)
Lastly, I want to say that the two hardest things to say in life are the hello for the first time and the goodbye for the last time.
Friend, the first thing I did already and I will not do the second thing in our life!

What a lovely sentiment (feeling) in this entry! I think you should revise the correct use of capital letters (particularly for the personal pronoun "I") and punctuation marks. They are important for maing your writing easy to read.

Best wishes,

Katherine