Is there a way to expand my storage space?

Can I somehow expand my storage space on the ps4 pro? If there's any possibility.

Replace the hard drive or connect to an external via USB3

Buy a larger hard drive or an external hard drive, basically both without problems.

Replacing a hard drive is also pretty easy, but you do not have to open the entire PS4, it is enough if you only deduct the upper part. Even easier is an external hard drive. Personally, but find an internal hard drive better, USB takes away space, is not stupid next to the PS4, tick is cheaper and a little quieter.

You can either install a larger (2.5 inches), or via USB a 2nd Connecting, as far as I know hard drives are supported up to 8 TB, that should be enough