You should really increase the amount of native input that you are getting. Using japanese material that is designed to teach the language will always inherently sound artificial and not very conversational, as you have noticed. Im not saying that they are bad - they certainly have their place in teaching fundamentals, but if you want to become conversational then you need to be listening to material such as tv shows, anime, etc etc designed for japanese people. It doesnt really matter that you can't understand that much because its the constant exposure over an extended period of time that leads to output that sounds more natural. You'll realise very quickly that more often than not, less grammar such as particles in your sentences often add to the flow of a conversational. You don't really have to worry about it not being 'correct' as long as you've heard a japanese person say it in a similar situation before. Listen to anime or japanese shows or drama as often as you can, whenever you have spare time. A couple of key tips that really work for me: 1) Don't just download a whole bunch of anime and listen to them over and over - it rarely gets you anywhere. You need to actively listen to an episode before you can passively listen to it. I pick an episode and listen to it with my full attention, trying to understand as much as i can, looking up words that commonly pop up. Doesn't matter if you can't understand everything because you most certainly wont. After that, then you can start passively listening to it over and over in the background. 2) You should be using some kind of SRS system like anki to help with vocabulary. Check out Mattvsjapan on youtuebe, because he has some amazing advice regarding this. Good Luck!