My goal is to attain bilingual-level proficiency in English. It's much, much harder than you'd think. My wife who is an English teacher at upper secondary school tells me a lot of her students think they're much better at English than they actually are. It's quite embarrassing really. 

Native speakers hear so much broken English from non-natives (and some less educated natives, although theirs is bad in different ways ) these days that they must have become desensitized to it to some degree. But if you want to be really good at writing and speaking in English as a non-native one thing you must do is eliminate gaps in your knowledge of idioms. For example, using phrasal verbs instead of their Latin-based counterparts is an important part of natural, friendly and conversational English.  Also, you have to acknowledge that your vocabulary is bound to have gaps in surprising areas if you only communicate in English online. 

I've read the Irish lost their language hundreds of years ago because knowledge of English was necessary for getting ahead in life in their society at the time. That is not a realistic scenario for us for a very long time, if ever, but there is some risk of English replacing Finnish in some areas in higher education.  I do not welcome that development. I pity the Irish. They are native speakers of a minority variant of English that does not enjoy a particularly high status. They'd be better off as speakers of English as a second language or bilingual.