I am currently learning German and Japanese at the moment. However I’ve noticed I don’t have time for both. So from now I will only learn one language at a time, but it’ll be more quality time. By the way I do not count the languages where I just immerse and chill into how many languages I am learning at the moment.
I’m giving myself a break from Japanese.
Cool.
It can be so hard to learn more than one at a time, you have to find a balance. I agree with a break and when you feel like you have got German cracked, come back to Japanese.
Feel free to still lurk and comment, good luck in your studies!!
As a kid growing up in New Brunswick, Canada, I was required to take French in public school from Grade 1 to Grade 10 to the point where I was fairly fluent. Having not used it for 20+ years, and studying Japanese for several years, I was terrified to find while travelling through Quebec that my French kept coming out largely sprinkled with Japanese. It’s strange how the mind works, but not as strange as the looks I was getting.
I experience something similar. In school, I had French classes for a couple of years, but haven’t used it ever since. Since this was 20 years ago, I’ve forgotten most if not all of that French. Now that I’m learning Japanese, I find myself randomly recalling French terms on some occasions and mixing them into Japanese sentences. It’s so weird.
It happens sometimes for me as well. When I took German classes around a year ago, Japanese unconsciously came out of my mouth sometimes. Needless to say, the Japanese students in the class were finding it quite funny…
i took german many years ago in high school/college, and I still think in the german way when trying to count japanese lol
It’s really strange how foreign languages can intertwine in one’s head. For me, native and English are solid and separate, but my half-baked Dutch is being overwritten by half-baked Japanese. I still understand it, but find it difficult to produce a complete sentence without any random Japanese mixed in.
It’s probably a good idea to focus on one language at a time. Give it time to solidify to the point where you don’t need any active study, and can just maintain it through entertainment (friends, TV, reading).
I always recall Russian words when I miss one in Japanese and vice versa, but they are not indeed competing. My head is just trying to fill the dots. 
The problems with learning languages together in my opinion are:
Went to Germany, wanted to ask someone for directions. Person didn’t speak English. My brain, rather unhelpfully, pushed Japanese out of my mouth. We were both rather confused.