Web API get data with multiple documents and save in SharePoint online list & library using CSOM.

Hello Guys,
I need to create Web API when user hits the web api then data along with the multiple documents save in SharePoint online list and library using CSOM object model. Please help me in it. Give me step by step suggestion to how we can create web api in sharepoint using csom and insert data in sharepoint list & library.
 
Thanks in advance!