Why are you studying languages?

I study three languages: eEnglish, pPortuguese and rRussian.

Proper nouns, including languages, need to be capitalized.

I started to learn eEnglish at school because it was a compulsotary subject.

Again, English is a proper noun and so needs to be capitalized. There was a spelling mistake with "compulsory".

It is important to understand and to speak eEnglish because it is a language spoken in all over the world.

You don't need "to" for the second verb, speak, as it can just use the one in front of "understand".

Again, English needs to be capitalized.

"All over the world" is better than "in all the world".

In aAdditionally, as I am a scientist, I have tomust read articles in eEnglish and to communicate in english with others scientists in English.

Next, I learn pI am studying Portuguese because my wife is bBrazilian, so. I am interested in her country and culture, so learning the language, country, culturean help me understand them better.

I think that pPortuguese is easier than eEnglish, as pPortuguese is closer to my native language (f, which Is French).

And finally, I study rRussian because it is an old dream of mine.

I like the writing and the songs of this languagRussian songs and literature.

It is important to understand and to speak english because it is a language spoken in all over the world.

In addition, as I am a scientist, I have to read articles in english and to communicate in english with others scientists.

Next, I'm learning portuguese because my wife is brazilian, so I am interested in her language, country, culture.

I study three languages: eEnglish, pPortuguese and rRussian.

Names of languages must be capitalised in English.

I started to learn eEnglish at school because it was a compulsotary subject.

It is important to understand and to speak eEnglish because it is a language spoken in all theover the world world.

In addition, as I am a scientist, I have to read articles in eEnglish and to communicate in eEnglish with others scientists.

"Other" is being used as an adjective here, not a noun, so it is not inflected for number.

Next, I learn pPortuguese because my wife is bBrazilian, so I am interested in her language, country, and culture.

You could omit "and" for a certain stylistic effect.

I think that pPortuguese is easier than eEnglish, as pPortuguese is closer to my native language (fFrench).

And finally I study rRussian because it is an old dream of mine.

"An old dream" on its own sounds incomplete.

I like the writingliterature and the songs of this language.

"Writing" is technically correct but sounds odd, because we would expect the reference to be to the act of writing (rather than what people have written).

I study three languages: eEnglish, pPortuguese, and rRussian.

I started to learn eEnglish at school because it was a compulsotary subject.

It is important to understand and to speak eEnglish because it is a language spoken in all over the world.

In addition, as to that, I am a scientist, and I have to read articles in eEnglish and to communicate in eEnglish with others scientists.

Next, I am learn ping Portuguese because my wife is bBrazilian, so I am interested in her language, country, and culture.

I think that pPortuguese is easier than eEnglish, as pPortuguese is closer to my native language (fFrench).

And finally, I am study ring Russian because it is an old dream.

I study three languages: eEnglish, pPortuguese, and rRussian.

I started to learn eEnglish at school because it was a compulsotary subject.

It is important to understand and to speak eEnglish because it is a language spoken in all over the world.

In addition, as I am a scientist, I have to read articles in eEnglish and to communicate in eEnglish with others scientists.

This sentence works, but you could rephrase the second half of your sentence in order to avoid using the word "English" twice, as it sounds a bit repetitive. I would do it like this; "I have to read articles and communicate with other scientists in English."

Because you are talking about reading articles and communicating with other scientists in the context of them both being things you must do in English, you can put those two phrases together in this way :)

Next, I learn ped Portuguese because my wife is bBrazilian, so I am interested in her language, country, and culture.

I think that pPortuguese is easier than eEnglish, as pPortuguese is closer to my native language (fFrench).

And finally, I am study ring Russian because it is an old dream of mine.

I like the writing and the songs of this language.

It might be good to specify what language you are talking about here, as you are discussing quite a few languages throughout this entry. Example; "I like the writing and songs of the Russian language".

This isn't necessary, but I think it sounds a bit more natural.