I am working on a wordpress theme but need to amend some text filed such as place holder texts and some other fields name need to be amended. Unfortunately, I cannot find where they are exists in the theme. Please need help.
Based on your question you are probably not building a theme from scratch therefore I would suggest you follow the instructions for building a child theme and as you make your changes a more detailed question may be pertinent to the message board
https://codex.wordpress.org/Child_Themes
Good Luck