I am doing German right now, and i used to be really worried about my speaking abilities as well. I wanted to get a native german speaking tutor to just practise talking with, but unfortunately there were none at the time. So, i got a uni student learning German. Sadly he didnt speak with that much ease, so it didn't quite help that much. I think that maybe if i had found a native speaker it would've been much different.
What really did help was going on exchange. There, i talked in the language constantly for 8 weeks. Now, i talk with SO much more confidence and ease. I'm not suggesting that you have to go on exchange to get better, but just that you need to constantly talk in the language (to youself or your fellow jap students) to practise. If you make mistakes that's ok, no one will judge you, you're still learning. Also, another benefit is that i have a whole bunch of German contacts with whom i can skype and chat with. I suggest that you can try and get a penpal (through the school? online?) and talk to them as much as you can! Skype and whatsapp are amazing for this.
To improve the complexity of your speaking, a native tutor could help. Also, try, for example, every week, focusing on a more complex grammar stucture (or whatever else makes your speaking more interesting/complex, i dont do jap) and create/write down some sentences using it. Then say these out loud, changing different elements of the sentences.Do this everyday - doesnt have to be for a long time - and try making up new ones as you progress, without relying on your pre-created sentences. Then try to link the complex grammar sentence structure you focused on last week with what you worked on this week etc, until you get a nice reportiore of speaking ability! It helps to talk about a topic too, e.g home, hobbies etc, whatever is in your syllabus
hope that helps!