Tell me about it! I’ve been studying since high school! (Granted, not well). I’ve lived in Japan! And yet reading has always eluded me. Probably because I didn’t study kanji hard enough. I have a distinct memory of leaving my final exam during study abroad, looking around town, and being like “oh THATS what that says! Wild! I could have read all these signs if I hadn’t crammed for exams and promptly thrown out any knowledge acquired!”)
And then I promptly forgot everything and am back here.
The difference between where you are now, and me in Japan, however, is I had the grammar and vocab to back things up - I was just missing the characters. So if you said “おいしさたいけつ！” I’d understand it, but if “おいしさ対決!” was written in an ad, I’d be confused.
All this to say, reading Japanese is pretty hard - honestly way harder than listening or speaking in my opinon - and at 4 months in you will be missing a lot of grammar and vocab, not to mention kanji. Before you spring money for a textbook, there are quite a few youtubers that cover Japanese grammar. Here are some that I will ~play in the background while doing something else~ cough I mean watch to learn:
These people all do lessons entirely in Japanese, but honestly its slow enough (especially at the N4 ish level) that even if you don’t understand them completely you can get through. While I personally don’t love her, a lot of people recommend Cure Dolly as well.
While some people can pick up vocabularly naturally, I’ve never been that person. I really recommend making flashcards, even physically writing things out so you can remember it. If you are lazy, Anki has a million and one Japanese decks, and there are also a million and one Genki/Tobira/Nakama/Insert College Japanese Textbook Here vocab decks on Quizlet as well.
Of course, as you start to read more you will start to recognize more. Using the sentence above as an example, you may say “hey wait, I know what おいしい means, what does it mean when the “さ” is at the end?” and then you can just look up grammar like that as well.
But at the end of the day you need a foundation to build on. And frankly thats where intro textbooks work really well. If you still find yourself struggling, I would just hop on facebook marketplace or amazon and get a used or older, out of print copy of genki and work from there. You will be reading light novels in no time!