Is it normal that some mods delete posts without explaining why? How is a new user supposed to learn from this?

I'm very new here on Reddit and am currently trying to follow the rules of different communities.

It has happened to me several times now that a post has been deleted without comment, without a reason, without a message, without reference to a rule.

I have absolutely no problem if I do something wrong. I want to understand the rules. But how are you supposed to learn as a new Reddit user when some subreddits don't give any feedback?

Is this normal on Reddit or am I doing something wrong?

I really try to post respectfully and read everything beforehand, but without info I don't know what to improve.

I would be happy if someone could explain to me how to deal with this as a newbie.