Muslims say Book of Luke contradicts 2 Timothy "All scripture is God breathed"?

I believe in my heart and faith that all scripture is God breathed and I have the words in my heart but don't know how to clarify it right when I speak to refute why I know it is God breathed. We do not debate it just simply discuss touchy subjects like these at times to learn more of each others faiths. Does someone have a way I can clarify why the Book of Luke is God breathed even though Luke states in the beginning of the book it was compiled from witnesses? Thank you and please no negativity. I am looking for intuitive and thoughtful answers. Thank you so much in advance.