Introducing myself.

Hi everybody. I'm a Piping designer for refineries and Power plants and work for a Spanish engineering company.  Currently I'm living in Madrid (Spain) but had been living in Mexico for 2 and a half years.
I want to improve my english conversation skills because it is necessary for my work.  My country is currently in a deep financial crisis brought on by the banks and this situation has been very bad for the young people. Many of us, possibly, are going to have to find work abroad in the near future because there isn't enough work here.
I'm looking for serious and mature english speakers that they want to exchange their native language with my native language on a 50/50 basis. I look forward to talking with people that they really want to practice and improve.

Well done!  As you can see I have made a number of minor changes and have broken up your second paragraph into 3 separate sentences.  One sentence was just too long for this amount of information.  Keep up the good work!

Introducing myself.

Hi everybody. I'm a Piping designer for refineries and Power plants working in an engineering Spanish company. Currently I'm living in Madrid (Spain) but also I've been living in Mexico for 2 and a half years. years and a half.
I want to improve my conversational english conversation because I need it for my work and besides, my country is in a deep crisis by banks and this situation is really bad to the young people, maybe many of us are going to have to work abroad in the a close future because there isn't enough work.
I'm looking for serious and mature english speakers that they want to exchange their native language with my native language 50/50. People that they really want to practice and improve.

Ahora, es más natural,

pero ,Su Inglés es increíble!