Best way for modification of ready-made scripts?

Hi, for some time I’m working on project which was made on the ready asset. I am tasked with modifying some mechanics provided by this asset. The problem is that there is no documentation for it and I waste a lot of time looking for dependencies between the scripts. Does he know any way to such a problem?

I also have a question if there is a way to check which script the object was created by

Talk to whoever wrote it in the first place?

Working on someone else’s poorly documented code is never easy.