Como melhorar o inglês depois do básico/intermediário?

Hi guys

This is my first topic here. Beforehand, I wanted to give for the staff my congrats because, it is great tool for us students.

Well, I've been studying english for over one year and I took some exams on internet to know which is my english level and in several websites, I got the ''intermediate level''. However, I'm able to read almost everything on internet until the time, I mean, texts, articles, some students' doubts on forums from internet and so forth..
My writing is good (I think so) and I do not think necessary to focus anymore in the grammar, unless someone of guys, show me a reason workable.
Now, in the last months I've been practicing my listening skill. This, on other one hand, I am having some issues but, there is no anything out of control, I'm just realizing that, that skill will be improved bit by bit.

Today, I usually practice my listening skill, listening to some podcasts and at the same time I usually reading articles in english, can it prejudice me?
I mean, would it be better I practice listening and reading, with audiobooks ?

Finally, I would like to know how can I improve my english level from this time, and also how many hours I must study these skills: listening, reading and writing ?

That's it.

Thanks.