I’d seriously look at resetting your account. I was at lvl 18 when my son was born and struggled to keep up for about 5 or 6 months. Reset the account which re-inforced all the early stuff, and meant I didn’t have to struggle with stuff which I couldnt remember at the higher levels.
You’ll be back to 13 before you know it.
I was in a similar situation a few weeks ago. I had just started back after a long time off and had over 1000 reviews to do. I just committed to reducing it by 100 or 200 every day until it was done. It’s hard since you’ll probably have forgotten a lot and all the ones you get wrong will be back in the review pile again soon. Just keep at it and eventually you’ll get it done. Whatever you do, don’t do any lessons until you’re done with the reviews and until you don’t have too many items in apprentice since those will show up as reviews soon enough. Good luck!
thanks everyone for your kind answers
so yup I won’t do any lessons of course,
I have the chance to burn a lot of stuff as well so that’s already some stuff less
@funkigreendog It’s an interesting idea (even if I admit to don’t like it , but I guess I wanted someone to mention it here aha)
is it possible to start over at level 4 or so ?
don’t want to do the “tutorial” again 
…
I returned after 700+ days to 700+ reviews. I’m down to 444.
Do more. Get them wrong. Read the info, get them right.
Get them wrong more often.
You could use [this script] to spend a week or two thoroughly brushing up on your existing levels, then jump into your reviews.
If you reset back to a level you felt fairly comfortable with, it’ll make catching up easier. I reset like 3 levels with 700 reviews and got 'em down quick once I put myself to it. And then the levels I’m now repeating are coming back super easily for the short time I worked with them, so catching back up to the level you were feels like a breeze. Just a 9 day+ per level breeze. ;D
Pretty sure you can request to be reset to any level. I realise it sucks thinking about starting over, but it was actually quite liberating.
I pretty much found I was getting 100% most review sessions up till level 10 or so. Definitely found it to be a relaxing and enjoyable way to get back into it.
Also allowed me to pace my levels, to ensure that I wouldn’t get a pile of reviews down the track all at once.
You can, and it will wipe everything down to and including that level. I took the partial reset route and you pointed out it felt like a really refreshing review. Before that I tried using the reorder scripts to go through reviews by level, but the problem I had with that is that some items were stuck in longer srs gaps so I couldn’t get a complete refresher that way. Partial resets are totally worth it.
wow interesting guys, so I may ask for a partial reset then…
i had 2600 review pile back at level 20, personally i just used a reorder script and slowly broke through it over a week or two, first dealt with the radicals and kanji, then as they repopped up i redid them as they were back in my memory. Then started from level 1 vocab all the way back up to 20, making sure each day i tried to get to a certain level of vocab, not particularly a certain amount. it was really not so bad after i just forced myself to do it instead of procrastinating. i felt the last 500 or so so easy as i was picking up motivation and a second wind so to speak
You could also try using the Anki style script. I often find it’s faster than typing out every answer, so it might help you break down the mountain of reviews more easily. Good luck, I’m sure you’ll manage fine! 
For future reference:
If you can afford lifetime subscription, buy it and put your account in vacation mode whenever you need a break. Vacation mode stops your review queue from getting bigger until you return from vacation. I don’t think “vacation mode” is a good idea for a time limited subscription because the vacation time is not added to your subscription.
I’ve had similar review piles before, and haven’t felt the need to do a reset. I never left for a terribly long time though, so it probably depends on how long you’ve been away, and whether stuff from earlier levels feels completely foreign again. But whenever this has happened to me, I’ve just started chipping away when I have time/setting aside chunks of time to hammer through a couple hundred reviews. I usually found that a lot of it was still there or came back very fast, and just moved into master/enlightened/burned status pretty fast. But if you try this, you are going to want to commit to just doing reviews for a few weeks to get apprentice/guru level items back down to a manageable number. But really, it’s not as bad as it seems, and a reset seems pretty drastic unless you’ve been gone for a good number of months and stuff from way back feels like you’ve never seen it before. Good luck!
Before taking the easy route of resetting, at least try tackle that review queue. It looks intimidating but many things in it will be really easy, you might be surprised just how many you know or need a little push to remember.
Really the more important thing to beat than the review queue is your laziness. One of the best ways to beat that (IMO) is to set up a schedule and stick to it, initially it feels like work but soon enough it becomes part of your daily routine. Might even help to attach it to some other routine, like doing it while eating breakfast,
I’ve just gotten through 900+ reviews. I didn’t want to reset as I’ve been over the beginner’s kanji so many times in other books and forms… so I just did what I could where I could. I’m lucky that I’ve got a fairly relaxed/kinda tedious job where I could rattle off ten or so every time the boss wasn’t looking. It’s taken me a full week though, and it’s going to come back to bite me when the guru/master brigade turn up. Just keep off the lessons until you’ve beaten the pile!
Just keep going, though, you can do it
What reorder script did you use? Can you recommend any?
This script! its really useful you can sort by many things, level or types or even choose which ones are priority
I’ve been in this situation a couple of times now. I tend to use WaniKani Reorder Ultimate script to order by level. That way, you clear out all the older stuff first. You will probably burn a lot of those or get them to a higher srs level so they won’t come back again anytime soon, so your overall review count goes down and stays down.
Keep doing that and continue chipping away at the reviews. Eventually, you might get to a point where you are on reviews for a somewhat recent level. Either you will continue to cut down reviews and eventually clear your pile, or you will start to get a lot of items you can’t remember. In the latter situation, I’d try to evaluate your options. Either continue with a low accuracy and essentially relearn through reviews, reading the info when you get an item wrong, or reset your level so you start back at the level where reviews start getting problematic, and continue from there in the normal way.
I did this twice now. Resetting from level 25 back to level 22, and just last week from level 26 back to level 24. In both situations I just felt like it would be quicker to start progressing again if I just went back and went through the last few levels again rather than continually working on a large stack of reviews I have trouble remembering.
I end up in this situation because I tend to do most of my reviews at work, but when I am very busy in work I tend to not do any reviews and let them stack up.
TL;DR - WaniKani Reorder Ultimate to order reviews by level, just keep working through them until you start to get a high failure rate, or you feel the items are becoming a bit too unfamiliar, then evaluate whether it would be quicker to reset your account back a few levels or continue hammering away at the reviews.
Wow so many replies !!
Thanks again everyone, I’ll try to make you all proud and clear that huge pile of reviews 
I just downloaded the ultimare reorder script you mentionned. Even if it was months ago I remember a lot of stuff so I think I will achieve it.
If not I’ll try to ask for a restart from level 6/7 i guess.
Thanks again and keep posting, it’s really interesting