Yes, I want to echo what bitpicker said. His written English is like native, you can safely trust anything he says about English. In fact, because he's making the effort, his English is better than that of many English speakers (who are notoriously lazy about grammar, grammatical rules and even spelling.)
I suspect he probably has a noticeable accent when speaks, but that's not relevant in a forum. But basically, he's put a lot of time into it, he's an absolute ace with grammar and additionally his experiences are relevant for anyone learning English.
Remember that English is MUCH closer to German than it is to Russian, so it's been easier for him to learn than it's been for you, for example. In Western Europe it's also much easier to get exposure to English and native English speakers.
For me, it's the same thing although in Scandinavia we have even more exposure to English than in Germany. I started from a really young age and I've lived in the UK for 10+ years. Basically, I am confident about my English and if I make any mistakes here, it's because I don't bother proof-reading most of the time, and because I change what I want to say while I'm in the middle of writing a sentence.
Unfortunately I don't know grammatical terms well and I am not as good at explaining the reasons why a certain sentence structure is better than another, as Robin is. The only English grammar I can remembers studying, is verbs: "go-went-gone" and "I am, you are, he-she-it is..." The rest I simply learnt naturally.
One little mistake is not the end of the world unless it's for a professional situation. I don't even particularly agree with the idea that everyone should have to speak English as a second language... As can be seen in International Politics, Science etc - as long as you've got functional English and can articulate yourself clearly without sounding like a fool... that's all you really need. Anything else is "extras". You should be aware that native English speakers usually think that foreign accents sound cool and interesting and they generally believe that the foreign speaker is intelligent since he masters more than one language (at least that is the attitude towards white people...)
I agree with everything that Robin said, although I wouldn't have expressed it as well. Translationsnmru is another forum user who is not a native English speaker but writes in absolutely perfect English and gives great advice.
I am trying to apply the same principles that he's outlining to learning Russian (basically repeating what I did for English). But I'm not so sure my approach is correct; Russian is harder and more different to any other language I know. I have not had the same practical incentive (necessity) to learn it, and nowhere near the same exposure. So I am not sure that the "English" approach necessarily works for learning Russian.... I feel that my learning is far too slow although it got a big boost by my trip to Eastern Europe (which is coming to and end shortly).
And I have a vertical hole in my brain where the information about grammar should be. For some reason I seem unable to pick it up and remember it. It's a real handicap when learning Russian and I am so in awe of people who can confidently speak about grammatical concepts.