Cimorene

Honestly, I can't imagine returning to a state of mind where I could read Kradam again, even in quite short doses. Otherwise I would be willing to look at what you were writing, so if you have something else easily accessible you'd like me to look at, I'd be willing. But I don't know how helpful that will be to you, because as much as I can continue trying to correct and explain the errors you're making, and I say this as someone who's learned my second fluent language entirely in adulthood, you'll learn much faster and better by immersing yourself in more English as much as possible.

In my case, it happened because 1) my sister-in-law gave birth to triplets and they needed a lot of help, so I was suddenly spending a lot of time with my in-laws surrounded by casual conversational Swedish; and 2) I needed to read a lot of textbooks, and hear a lot of lectures, in Swedish for university. But the latter, while it helped improve my esoteric vocabulary, didn't do a tenth of what the former did for me. It's hearing the language in a variety of situations and carrying on a variety of conversations in it yourself that really makes the biggest difference in mastering the language, because your language brain soaks up not just words but expressions and contexts and how-do-people-say-this and what-do-you-say-in-that-situation and grammatical structures and idioms like a sponge. It's why they push becoming an exchange student as the best way to learn languages, no doubt (it's probably pretty similar, and a much easier and less permanent way to acquire a foreign family than marrying into it :)).

So, I mean, I don't know where you live, but wherever that is, you probably can't just plunge yourself into the daily life of an English-speaking family, but I do think reading (surely you can find something, textbooks or non-fiction or newspapers, biographies of people you stan, whatever).

The thing about fanfiction is that the quality isn't at all dependable. Of course published fiction has a wide variety of quality, including things that could pass for bad fanfiction (Stephanie Meyer), things that are just plain bad (Dan Brown), and things that actually have grammatical errors that editors apparently didn't bother about. But there's still a baseline level of comprehensibility at least, because they do pass through a professional editor's hands - even if that editor isn't necessarily completely on the ball at all times.

There are some quite long and complex Kradam stories with a very high level of quality, but in every fandom the stories which are similar to published novels are outnumbered by the plebefic - the things that wouldn't make the cut - the slushpile. And if you're reading fic that's full of errors, or even written by other non-fluent non-native speakers, then of course it's not going to help you in the same way. But that said, while reading is the best way to learn the finer points of writing, TV is still probably more useful for language learning. Goes in through the ears, into a different part of the brain, and probably sticks better, unless your brain is quite atypical. I advise you to find some television show that's got like 10 seasons or something and just start at the beginning and go through to the end, perhaps watching while you chat or do other things around the house or something.