how can i unify the line-height to make it looks more beautiful?
If this happened as a result of drag'n'drop then I'm not sure if it can be resolved without just creating a new doc and re-doing it.
Sorry, what I meant was to open a new doc and type it afresh and format it as you like. I said that if you had dragged the text and dropped it onto the doc as the very same thing has happened to me when I've mixed fonts and font sized and then tried to format it all the one way.