As @SleepyOne said, it would be good for you to start grammar soon. Many of us were learning Japanese, including grammar of course, before coming to WaniKani. There’s no real reason to wait. It’s just a matter of finding the right balance.
This happens to me as well. I think the best solution is to read as much as possible. Writing can help too, but unless you get your writings checked you risk practicing mistakes and forming bad habits.
For this I recommend the script Jitai, which randomizes the font during reviews. You can even install additional fonts on your computer and add them to the script for more variety.