Juliana, congratulations on your work. It's amazing that you are trying to learn English on your own! I have a couple of suggestions. 1. If you are answering different questions, separate the answers. I cannot tell from your writing where your answer to the first question ends and where your answer to the second question begins. 2. The next time, the best thing to do is to put this in the exercise section, not the question section. That would mean writing it out, of course. In the exercise section, there are tools for people to help edit and correct.

You wrote: I agree with this statement, but if a student want to study in a different culture, why not. Perhaps, it is his dream. Many students want to learn new culture an different country, and if they really want it. They do anything to achieve their goal. It’s my opinion. my corrections: I agree with this statement, but if a student wants to study in a different culture, why not. Perhaps it is his or her dream. Many students want to learn about a new culture and live in a different country. If they really want to do this, they will do anything to achieve their goal.

You wrote: My advice to anyone who goes to university. It is before that goes to study a board, you should know that is difficults, and you just need to understand why you goes to university, it is important for me. Corrections: My advice to anyone who is going to university is: before you go abroad, you should know that will be difficult. You just need to understand why you are going to university. (you can also say "attend university')

I will correct some of your work here. I am going to concentrate on the second question:
2. What are factors which are related to academic success in high-school students? 
 This is what you wrote: Despite, many factors may related to academic success in high school students. For instance, other students can related to academic success. For this reason, student might to not believe in yourself efforts and may be unmotivated. But this have many good factors. To begin with, family. They can to support their student, and give students motivation. Secondly, is can be student a future goals If they have their future goals, why they study. They can have motivation to learn new and to achieve their goals. In my opinion, there are many factors which can related to academic suces. And for everyone factors is different. Here is my correction: There are many factors that affect academic success in high school students. For instance, other students can play a role/can affect students' academic success. (you can say 'students' peers' can affect their success). For this reason, (unclear -- what reason?) students might not believe in their own efforts and may be unmotivated. There are many things that have a positive impact. To begin with, family. They can support their child, and give students motivation. Secondly can be students' future goals. If students have clear goals, then they may study more. Theywill have motivation to learn new things to achieve their goals.

They can support*. Can doesn't need the to here. A lot of the mistakes are related to wording which interacting a lot with English such as watching YouTube in English can help. If you want to practice your English, I am a native speaker and you are welcome to send me a message anytime.