If you mean that there used to be two companies that became one, then use the verb consolidate and the noun merger
The company was [established as] a merger of two Turkish companies conslidated in order to undertake works in Romania.
Unless you meant: "The company was established by two Turkish companies in order to undertake works in Romania." = "The company was established by two Turkish companies participating in works in Romania." oooor "The company was established in effect of two Turkish companies' participation in works in Romania."
The expression "for some reasons" sounds too informal for a CV, I would leave the sentence as:
In March 2003 the shareholders decided to dissolve the company.
Or to make it all shorter:
The company was a merger of two Turkish companies conslidated in order to undertake works in Romania and later split by shareholders in March 2003.
I hope that helps, keep in mind I'm not an English native speaker though. Good luck with the job :)