Hi Andrew. In my opinion, we have two ways to learn, and imersion one of these, it works when you feel the need, the difficult you're struggling makes your brain to force to understand and it seaches ways to do that. At the same time. In other hand, imersion need to be structured for learning. At the same time study vocabulary outside by yourself help your imersion session.
This is I am telling about:
1 Imersion need to have a context
2 Context need to have vocabulary
3 Pretending contexts, using vocabulary, you will feel confortable to learn, not stressfull.
Many years ago, I went to work in a Pilotage, this was new for me, and my interview was in English. When I got the job, my english was not proficient, and the CEO told me, you need to learn the specific English for Pilotage, because you need to speak tecnical language here. In this case, I was in imersion, talking to vessels from all over the world, I had context and I only needed to find the vocabulary, studying books of tecnical vocabulary i got to keep my job for long time. When I went to work in a hotel, I did the same, studying vocabulary a lot, and possibles phrases as well.
My advise for you is: don't worry a lot, it's a process. Create a context with your teacher (shopping, going to bakery, working in a farm, etc) and study that vocabulary for while. You do not need to be perfect, in the beggining comunication is the way, even with mistakes (as I certainly did in this text).
I hope you find a confortable way to learn this beautiful language