You can backup PS4 data onto an external drive, which is a great way to free up space. But you'll need to backup your trophies separately.

Which external hard drive is best for PS4? As the complex worlds of your favorite video games become larger, so too does the amount of storage space games require. Games like “The Last of Us 2 ...

The PS5 will be capable of installing and playing PS4 games from an external hard drive containing the titles downloaded from the current generation console, Sony and PlayStation has confirmed ...