I just leveled up to level 11, and I feel like I’m spending all day on WaniKani and I still can’t keep up!!
Please help, is there anything I can do?
You can regulate the amount of reviews you have by the amount of lessons you do.
While it’s always tempting to do all the new lessons in one go, it could lead to overwhelming amount of reviews later
Luckily, WK does allow you to choose the lessons you want to do right away with the “Advanced” button n the “Lessons” widget.
You might even want to stop doing lessons for a while and concentrate on cleaning your pile of reviews first.
I hope this helps… Anyway, best of luck with your studies! 
There isn’t one way to do WK. it’s better to do less and continue than try to do lots, drown in reviews, and give up. I generally only do WK once a day and try to zero my reviews then. If my review numbers get unmanageable, I don’t do any new lessons until my review numbers drop down again.
At the start I gave myself 3 years to get it done. Some people have taken longer. You don’t have to do it in a year. I wanted to have time to do other Japanese studies not just WK so I’ve taken the scenic route.
I’m 3 years in and ~75% through, which means I have (at least) another 2 years to go! I’m running it like a Software Project: the first 90% of the work takes 90% of the time; the remaining 10% of the work also takes 90% of the time.
Currently my setting is 9 new lessons a day but I take that as my maximum, not my goal. I plan to do 4 lessons a day some of the time, including 2 new Kanji just to keep it ticking over, while I catch up.
So: just slow down your lessons and you will be grand!
The same issue, when you slowed down, numbers of review is growing and I don’t want to go through 300+ cards another time..
Stop doing new lessons until your review pile gets to manageable numbers. And then adjust your new lessons per day down. Every x lessons / day will generate a multiple in reviews over the long term. (which will keep growing until you start burning items). It’s tempting to do more lessons early when there’s not many reviews. And that’s fine, if that’s what you want to do. Just be aware that every extra daily lesson will blow up your daily review pile over the next weeks / months.
If you do 300 reviews in a day, expect 200 reviews a week later. If they’re all bunched up on the same SRS level, if you do them all at once then they will all come back up at the same time. If 300 is too much, stagger them maybe 75-100 a day.
I can recommend what I am doing when reviews pile up. Do a fixed amount of reviews per day, for example 200. No matter how many are waiting. It will eventually clear out and this way you don’t create spikes in the future.
What I’ve been doing is 15 lessons a day, but only up until I have 100 items that are at apprentice level. For example, if I have 90 apprentice items, I do 10 lessons. If I have 80 apprentice items, I do 15 lessons. Even when I have the time to do far more lessons, I don’t. Because even if I have the time to do 50 lessons one day, that doesn’t mean I’ll have the same time to then consistently review those items on the following days. You can always adjust the numbers to fit what works best for you