First just want to say. Kudos for being ambitious! Whatever the result is, hopefully over the next few months you will have the chance to improve significantly your Japanese knowledge.
And sorry for this wall of text:
From today until the exam, try to read something every day. Eg Bunproâs reading section / NHK web easy articles (some have audio too for practice and shadowing) and / or easy stuff from Satori Reader. If possible copy on paper something eg first 4/5 sentences. (Personally writing on paper helps me remember and understand more). Reading is like a muscle, the more you can read and for longer, the better.
Bookwalker,jp or Booklive could also be used towards the end as (nearly) everything has free samples = lots of reading practice.
Getting something like Kanzen Master N4 grammar book and reading book would be beneficial. Lots of practice. There are also drill books that test all sections (not just part of the JLPT exam). There is quite a lot of question videos on YouTube too depending on your budgetâŚ
If you can go through the grammar points on Bunpro: 100 % N5, 100% N4 and start the first 20% of N3âŚ. (There will always be unknown things on the exams and there are always changes with the JLPTâŚthey sneak in grammar from other levels haha). If you can do all N5 grammar points and 70% of N4, it should be enough. Bunpro has a lot more grammar points than other resources.
There are 107 days or so until the examâŚ.
Day 0 to 30ish:
Probably it would be a good idea to try to spend the next 30 days or so to build up your kanji, vocabulary and grammar knowledge.
Next, (if possible) try to have a mock N4 exam. 10 minute breaks between sections. Just to see where you are at and what it would be like to take the test
Day 30ish to Day 60ish:
The next 30 days, I would slowly start to do practice questions (leave listening questions for later when your vocabulary has become better). I would still mainly concentrate on building your kanji, grammar and vocab at this point. (Eg start from N5 practice questions and move slowly to N4)
(By doing lots of practice questions, hopefully the common vocab / kanji will be easier to learn and you will get used the JLPT specific way of using Japanese)
Day 60 to the end:
From here until the exam (a month and a bit left), start to do listening practice questions too and if you wish more listening in Japanese eg Japanese news (on youtube ANNnewsCH ) , podcats ( eg Sokoani). Try N3 listening questions too. Normally that section is a bit harder than on practice tests
During this last month, If you can try to do as many mock exams as possible. Hopefully you will build some kind of mental fortitude. I remember some people lightly dozing off during the listening section⌠hehe, I took the exam in Japan in July right when it was the hottest day so far in my city haha.
Reviewing should become more important towards the end.
In the last week, try to relax more. On exam day, just enjoy the experience. For me at least it was a lot of fun (even if lightly stressful hehe).
Anyway good luck, hope this wall of text can help.