I can't say for certain why your post was removed as I didn't see it. I am also not a moderator. But I think the best reason as to why your post was removed was because it has probably already been answered in an existing pinned post (its possibly a frequently asked question) or it was deemed not relevant to the board it was posted in.
Did you try searching for an answer to your question before making your post?
Yes, i've made some basic search before posting. But anyway,even if I have missed smth, shouldn't I get a notification regarding eason of deletion?
If I do not know why my post was deleted, how can I know where is a mistake.