The phrase "big help" means that someone or something has provided significant assistance or support. It suggests that the help received was important and made a meaningful impact. Full definition
Former real estate clients turned out to be big help in getting the product ready to market. (realtormag.realtor.org)
This is the great age to start because at young age you will be learning a lot of things that would be of big help for you when you start driving your own car. (wannadrive.com)
And at any point, having the files app has been a very big help with a lot of productivity tasks. (themrphone.com)