Question about Seagate FireCuda 520

No, not directly.
Apple uses "proprietary" connectors for its SSDs.
Here is a guide:
https://beetstech.com/blog...

For iMacs, for example, you can use adapters like this one (I've done it myself with the same SSD for a 2015 5K iMac):
https://www.esons.ch/pi...

But for macbooks, I'm not sure if there is enough room for the adapter in the case. it's tight in there ;)

Good luck.

Hi, normally yes, the 2015 MacBook still has the option to upgrade the SSD with a new one, they are 2280 size in the 2015 Macs.