A2485 MBP2021
Is it possible to upgrade the fitted SSD from 512Gb to 1Tb or higher ?
MacBook Pro (2021)
Not if you already purchased the laptop. The current Apple laptops can no longer have their memory or SSD storage upgraded after purchase. The same applies to many desktop Macs as well. If you need extra storage, then invest in some external storage or purchase another laptop which will have sufficient resources for your needs.