Great summary :)
I'd add up a couple of things, though:
1. Avoid asking people questions of general preference, like "which is the best language". Rather, describe what you want to achieve and then perhaps ask for the best tool or solution to do that.
2. The forum is run in English. People often downvote non-English posts, especially non-Latin ones (sorry, tough luck). In order to avoid that, mark your question with [XX] where XX is your ISO language code - [PL], [RU], [TR], [ID] and so on. It gives people information that you probably won't understand the answer in English, and those eager enough will make an effort to reply to you.
3. RTFFF - Read the freaking forum first. Be realistic - in such a great community there most likely was someone before you, who had the same or similar question or doubt. Too many threads are about the same topic already, don't add up your own, just because you're lazy :)
4. Mark best answers as best. This is not only a good manner, but it makes the person who made an effort to reply to you happy and gratified. For most of occasions - it is one of the only decent (xp-wise) rewards for high-experienced users to achieve some xp boost.
5. Don't cheat in any way. Sololearn community won't tolerate cheaters. Codes are free, but don't appropriate them as your own! Always leave the author's credentials and do not to publish the codes, leave them as private. Also, don't run fake accounts just to win some challenge xp - will be noticed in a second :)