Yes, once you log off completely and them log back it, you can’t edit your post. It’s best to check out (proof-read) your posts before saving them. That’s what I usually do.
Since English isn’t your native language I wouldn’t be too concerned about grammar and spelling in your posts. As long as it’s readable it’s fine. I don’t think anyone will disrespect you for grammar and spelling errors. If they do just ignore them. I have read your posts and your English is really good. I wish my Spanish was as good as your English!