I tried to edit one person post but I couldn't edit. What's the reason behind it? When will I be able to edit someone post again? From where to know when I can edit someone posts.
Most your edits have been rejected, as they are too minor and only changed one word or tag. While sometimes this is important - most times change more than one thing (not just 2 tags, find some spelling/capitals in there as well) until you have the privilege to edit without suggestions.
Other times you have introduced information - that should be presented to the user as a comment such as https://askubuntu.com/review/suggested-edits/182255 or https://askubuntu.com/review/suggested-edits/181755
Based on - https://askubuntu.com/help/editing you will need to wait 7 days.
Additionally, any user who submits many rejected edits will be banned from suggesting further edits for 7 days.