Hi, just to clarify I’m no expert but I can give you some ideas. It might be good to get an idea of what level you’re at now, so you could take some TOPIK mock exams, look through the contents page of a grammar book or something like the TTMIK curriculum list to check which grammar points you know and don’t know. You could even get a teacher on Cafetalk or Italki to evaluate your level and areas you need to improve?
The way I study is to consume and use Korean as much as possible and then check online for anything I come across that I don’t know. But if you prefer using books you can probably do the same if you have a big grammar reference book. I would just try to check your level and identify your needs. If it’s your grammar that’s scattered then go through lists and top up any grammar patterns you missed out on learning, or get books specifically focused on the skills you need to improve. Also maybe have a goal in mind. When you say “finish” and “fluent do you mean capable of in general conversation? academic Korean? Korean for working in your specific field? Then you can ‘top-up’ parts of your Korean that will be most helpful to you.