This so much.
I get the desire for feedback, @Napolethanos, trust me. But I didn't start writing in English until I've had 9 years of practice in my first language. Add to that the fact that I studied both my languages in university, and you have all the skills you need. Easy!
All jokes aside, writing in any other language than your own takes skill if you want it to be any good. I don't know if there are any forums in your language about fan and/or writing stuff in general? It helped me a lot to just have a community where I could indulge myself with characters and headcanons and whatnot. I practiced along the way, all fun and games, no pressure and no strings attached.
My studies in both German and English came afterwards, and THAT made me think, "hey maybe I could do it in English, too" (since I don't like the German publishing industry at all lol). So I can't really offer you resources like the others did, as I simply... don't use any except dict.cc, linguee and my Mac's Oxford Dictionary for cross-reference—Grammar is more or less etched upon my bones now thanks to some very good teachers and professors. xD But for the occasional check-up on idioms, Merriam Webster is a good resource, too! But for that, you kinda... need to know the idioms, so again, it's only for cross-reference. Still helpful as hell, though.
If you really, really want to understand the language in order to write fluently in it, you won't get around having a trusty Grammar resource at home. Try English Grammar in Use by Raymond Murphy; it comes with a learning disc, and it covers EVERYTHING. Then, practice. Read a lot, watch contemporary movies and TV series to make yourself acquainted with idioms (I know more American ones, so I stick to American English in my writing), and then: just do it.
I can tell you, though, even with all that work? You will struggle. I'm far from being on a native level, even with all those years of studies under my belt. So when I write, I still put my native idioms in brackets for the rough draft, and then build around that when I edit for publishing.
It's... not easy, to say the least. So you need to know what you're getting yourself into here. :'D But as far as I am concerned, it's totally worth it.