Two years ago I started learning Japanese!
This year I started studying Spanish!
I am facing the struggles of learning a langauge, just like you. Let me explain...
I keep mixing Japanese and Spanish in the same sentence when I speak! I also use Japanese grammar structure when I speak in Spanish.... oh no!
One technique I have discovered is to separate the days that I speak the languages. For example: on Mondays I only speak In Japanese. On Tuesdays I ony speak in Spanish. I have realised this really helps!
Is anyone else studying 2 languages at the same time. What are your techniques to avoid getting confused and mixing languages?