Hello there, so I have a question regarding a loft of multiple curves. I am trying to take another surface and re trim with the loft except when I try to do that what happens is there is an error I would just like to understand the solution or what went wrong . any guidance will be greatly appreciated . image|690x437
Because it is red 
@Michael_Pryor I see that it is red and it mentions there is an error regarding the surface and even then I try to re trim the surface, this is what happens
Read the link he gave you 
Then read also the “c” input description (to the very last letter)
Plus the “c” input of the loft component asks you for multiple section curves.
In the “very shy and lonely” picture you gave us, we can at least see that you only are feeding one curve into the Loft.
If this doesn’t solve it, please read carefully the “effective question” and post a complete and detailed question with files.
I apologize on my part. I have used multiple curves to loft . I have scaled the curves accordingly to the graph and then have loft but now that i want to retrim its just that the loft is not a surface
Well, A brep is not a surface. There is your problem.