Learn Russian or German or both
I am currently learning Russian and struggling a lot, but I also really want to learn German, what is really best continue with Russian, put it on hold and learn German and go back to Russian or both at the same time?
If you're struggling with Russian, I suggest redoing the lessons you have the most difficult time with until you know it then moving on :)
If you wanted to, You could do both at the same time, but many users will generally recommend learning only one at a time. I prefer having two so when i get an unmotivated streak for Spanish, i can always do a few Vietnamese lessons.
Since they're pretty different I think you could do both at the same time. However it will probably take you longer to get a working knowledge of both since you'll be dividing your time. I also try to avoid learning my different languages too close together so I don't want to keep thinking in the other language.