I don't see anything in the product description or manual which indicates that you can load new sounds:
https://www.roland.com/us/products/gw-8/downloads/
https://www.roland.com/us/support/by_product/gw-8/owners_manuals/
And even if you could, I doubt that you'd be able to import sounds from a Korg. Most keyboard manufacturers are protective of their sounds. If Korg (or other manufacturer) wanted people to be able to load the sounds from a Korg keyboard into some other brand of keyboard, they'd probably be selling CDs of their sounds for loading into other keyboards, sample players, etc.
If a particular keyboard lets you import new sounds, the manufacturer will usually have new sound packs available for you to buy-- so if you can't find any such packs for sale for a particular model, that's one indication that the model doesn't have the ability to import new sounds. For instance, many of Yamaha's PSR-S and Tyros models let you load new sound packs. Note that different models don't have the same amounts of memory or all the same tone-generating capabilities, so a sound pack for one model might not be compatible with other models.
And some keyboards even let you create your own sound packs-- e.g., some of Yamaha's high-end PSR-S and Tyros models let you import user-sampled wave sets, sound fonts, etc. But it's my understanding that creating a new sound pack can be a lot of work, since (as I mentioned in my reply to your other post) a given voice or tone might use multiple waves layered together, or a number of different samples per note depending on note velocity, as well as each note having its own sample or set of samples. Nevertheless there are people who create new voices or tones for their keyboards.