What can I add to improve my English?- Please check ("What" implies a question so you need to use the question mark to indicate a question)

It has been a while since I haven't wrote written here.
How am I doing? I got have headache, a sore throat, and a cold etc. I hope that I am not going to nna die. That made me Being sick has made me miss 4 university days. Hopefully except for being out sick that, everything goes well .... (goes well with what? exams? this is an incomplete idea) 

How is my English doing? I guess it is a little bit better: From now on, in addition to my courses, I am going to  used to participate to in "Le café langue". This is a place where people meet each other and have possibility to practice English or other languages around a table. It's really a fulfulling experience, you practice, and you get to know other people (students, workers, teachers and so on). It takes place twice a month. Also I have all Thursdays, 2 two hours of extra courses with Erasmus students taught by an American teacher. I'd like to experience Erasmus next year so It this situation feels like a repetition for me. (The intent of your last sentence is a bit unclear; rephrase or use native language) 

That's it, I think I'm done, it's good to write from time to time. Thanks for reading me. :)

I have the following suggestions:

Keep the sentences as simple as possible

Break complex ideas into multiple sentences

Replace numerals with words ('two' instead of 2)

Capitalize all proper nouns (http://www.grammarbook.com/punctuation/capital.asp)

Try to write formally when learning the language rather than writing as one might speak (so avoid writing 'gonna' in deference to using 'going')
Avoid catch phrases and contractions (like 'can't instead of cannot or 'I'm' instead of I am, unless you are writing informally)

You can always learn colloquialisms after you master English.

What I add to How can I improve my English - Please check

It's been a while. I haven't wrote written here.
How am I doing ? I got headache, sore throat, cold etc. I hope, I'm not gonna die. that That made me miss 4 university days, except that, everything goes well.

How is my English doing? I guess a little bit better: From now on, in addition to my courses, I'm used to participate participating to in "Le café langue", a place where people meet each other and have possibility to practice english or other language languages around a table. It's really a fulfulling experience. you You practice, and you get to know other people ( students, workers, teachers and so on). It takes place twice a month. Also, I have all on thursdays, I have 2 hours of extra courses with Erasmus students taught by an american teacher. I'd like to experience Erasmus next year so It it feels like a repetition for me.

That's it. I think I'm done. it's It's good to write from time to time. Thanks for reading me this. :)

You are doing such a great job with English. Keep working hard on it. I know it's difficult to learn another language but you are doing an amazing job! :)

What should I add to improve my English?- Please check

It's been a while since I  I haven't wrote on here.
How am I doing ? I've got a headache, sore throat, cold etc. I hope , I'm not gonna die , This has that made me miss 4 days of university days but except apart from that, everything goes is well.

How is my Englishdoing? I guess a little bit better: From now on, in addition to my courses, I'm used to participating in "Le café langue", a place where people meet each other and have a possibility to practice English or another language around a table. It's a really a fulfulling experience, you practice and you get to know other people ( students, workers, teachers and so on). It takes place twice a month. Also every I have all Thursday I have 2 hours of extra courses with Erasmus students, taught by an American teacher. I'd like to experience Erasmus next year so it feels like a repetition for me.

That's it, I think I'm done. It's good to write from time to time. Thanks for reading me. :)

Hey. Nicely written. Just a couple of points to help you:

1) In English, everything is good or is well. It can't go well. 

2) Try to avoid using too many commas in your sentences. I think you can join up a lot of the sentences or even start new ones.