I exactly know how you feel. I also struggle sometimes to find the right words to express myself, especially during more formal conversations. I don't think it's conversation that we need to practice, though, but the vocabulary needed for such conversations. Therefore, the best way to improve your conversation skills is through studying vocabulary, especially words that might be useful for you during interviews.
What I find helpful is making a list of words that I select from various situations, during which those words were needed to express myself. In other words, after such conversation, I take a moment and try to come up with the words that I wanted to use (in my own language), then if needed, I look them up in the dictionary....sometimes I don't even have to do that, since I do know the word, but during the conversation it was not there, which means to me that this word is not remembered well enough...then I try to use those words in context, or write a story incorporating them. After a while a find myself using the words I learned and having less and less problems with expressing myself.
Of course, it would be better if you had someone to talk to and practise your conversation, but from what I understand you don't know anybody who could help you that way. Try my method, it works well for me, so it might work for you as well.
Originally Posted by RMM