There are apps that claim to "clean up" your Mac for you. All I can say about those is never install any app that claims to “clean up”, “tune up” or “speed up” your Mac. These apps exist for one reason: to extract money from the wallets of the inexperienced user. What they do can be done in other ways, and mostly what they do is unnecessary, but sounds good. Unfortunately in the hands of an inexperienced user they can do a lot of damage to a Mac OS installation. Avoid.
What are these old and unnecessary files anyway? How could any app know what you consider old or unnecessary...