Hey Laura, I would say they are more formal, but that is not to say that "because of" is informal. I think "because of" can be either, but "Due to" and "owing to" sometimes sound more elegant or gentle, depending on the context. Often in an official setting, we use the other two to deliver a message more politely - "my mother had to leave the wedding early due to an emergency" might be preferable to "my mother had to leave the wedding early because of an emergency" which is still polite, but less elegant you could say. I'd say the difference though is very subtle, and some may actually disagree with me on this. I think best think of it as different ways of saying the same thing - so that you can vary your language and not repeat the same phrase over and over. Also Andrew is correct - "due to" does not have to follow the verb "to be" e.g. she left due to an emergency

Is it important to get a certificate?

Getting a certificate is a good decision, in case we want (alt: need) to prove what our level in English is (style point: we don't end sentences with a verb). Those documents don’t prove that we’re fluent in English though.

These kind of exams that we need to pass to get a certificate involve questions to meassure our listening, speaking, reading and writing. If someone is good at those skills in their target language, they’re probably close to fluency. However, we have to remember that it’s still an exam which means that we don’t need to be fluent in our target language to get a high score. For example, when we were in school we probably had one subject that we hated. If someone didn’t like biology, they would try to memorize the topics the night before, and then pray to remember them in the exam. Sometimes, this way of studying works, other times it does not. In case When it works, we’ll probably forget about those topics because our real goal was to pass the biology exam rather than learning (verb conjugation here should match the conjugation of "pass") something about biology.

Another reason (for what? unclear for what point you are giving reasons. Repeat it here to be clear) has to do with strategies in exams. if our purpose is to get a certificate, fluency can be replaced for by a good strategy. Techniques for reading, listening or filling in the a blanks  gap (alt: gap fills. Both are the names we give this activity) in order to get a high score are important in those exams. I know it this because I was enrolled in a language school where the professor was really focused on teaching those techniques.

In my opinion, certificates are important and useful as long as we need a document that speak for us that demonstrates we have a great level in English. Although, the benefits and challenges that mean learning a language should be more important for us ( I don't understand this sentence).

Whiteboards

In my spare time, I always think about how to take advantage make the best use (many alternatives) of my time (Style note: we try not to repeat the same word in a sentence twice, as you do here with "time"). Suddenly (I know what you mean, but we don't use suddenly this way exactly. See my suggestions in blue) Whenever I spontaneously/randomly come up with ideas for this, pop up into my mind and I write them on my whiteboard.

A few years ago, I put a small whiteboard in my bedroom because anyone used it (do you mean "so no one else could use it"?). In the beginning, I used it for reminders. I just wrote down some activities that I was going to do. Then, I began writing some words or expressions in English that I wanted to become familiar with. For example, if I found a new word in a book, I’d write it down on my whiteboard. In this way, every time that I looked at it, I’d revise the expressions. It worked for a few months until I got an app on my smartphone that helps me remember words in a better way. I still use the whiteboard for writing coloquial expressions, or to remind myself about the prepositions used with certain words. Unfortunately, there wasn't enough space on my whiteboard for writing down many expressions. Furthermore, my whiteboard was a totally mess because in many cases I was in a rush so I wrote as fast as I could. However, now that I've begun doing so (doing what? You have to say, it's unclear) in a word file on my laptop, I thought about what I was going to do with my whiteboard.

Today, I decided to use it to build mind maps for planning my activities and future essays. I usually do such brainstorming on a sheet of paper, but I hate having many documents on my desk. I prefer to use whiteboard markers, and to then get rid of what I wrote with them.

Anxiety

I’ve been having problems with expressing my ideas clearly in the past few years. It's not so much that I’m shy or have problems giving my opinions in public, but rather that I sometimes can't explain my ideas as well as I wish.

I’ve noticed this problem in three different situations. First, I find it difficult when I try to explain my point of view when confronted by an open question from a professor, because sometimes in the middle of my explanation suddenly I suddenly get lost and forget what I was going to say. Second, in some presentations I get a little nervous during presentations when things don’t work out as planned. In this case though, I think it’s normal to worry when you’re not ready for a presentation. Finally, I have problems with talking too fast, which has happened in many of the conversation exchanges that I’ve had so far. When speaking at such a speed, it becomes harder to create sentences than when you’re calm.

In my opinion, the main reason why I feel anxious, at least in the classroom, is that I’m afraid someone else will bring up the same idea I was going to mention, and then I will have nothing to add to the discussion. To solve this issue, I just try to take a deep breath before speaking and try to be sure of what I’m saying so I avoid the typical phrase “are you asking me or telling me?” (I don't really understand what you mean by this phrase... can you explain?). I’m also looking for a good self-help book on this topic anxiety (I recommend mentioning the specific topic here, for it can be unclear) for more strategies on dealing with this issue.

Doing things quickly (alternative: Doing things in haste)

Lately, I haven't had enough time for the activities that I try to include in my everyday routine. Some of these are learning Portuguese and English, studying in college, and taking the courses required by workplaces where I want to work. That´s why I’ve been doing things so quickly.

My typical day starts really early. I have English classes in my city at 7am, so I wake up at 5am. The place (language school?) is about 30 minutes from my home. Then, I come back home at 9am. The first thing I do when I'm back is my language listening practice. Currently I’m listening to an audiobook called “The Girl on the Train,” which is a thriller. After doing this, I write an essay in English so I can practice my writing skills. I usually write about something that pops up into my mind when I´m bored on the bus or in university classes. In the last few weeks, I´ve also been talking to a native English speaker. We don’t speak at the same time throughout the week, but I try to speak with him/her everyday. By this time it is usually late in the day, so if lunch hasn’t been made yet, I do some lessons on Excel on the internet. Otherwise, I’m having lunch as fast as I can in order to make some time for my 30 minute piano lessons. Once I’ve finished with that, I have to go to college for some boring but necessary classes. If the classes are at night, I arrive at home at 11pm or so. I have dinner and then my day is over.

Sometimes though the classes are in the morning, so I just do the same activities a couple of hours later. My activities related to learning English are pretty similar to learning Portuguese, but in the case of Portuguese it takes me less time (question: why?). I also read books in both languages but this often happens randomly.

Note: Not all the changes I made are corrections. Many are improvements to style, to make the phrases sounds better.