upgrade RAM on macbook pro

The only way to do that is the same way you upgrade the engine in your working car to a bigger one.

You convert your current Working device to CASH by selling it, and use the cash to buy a device that better meets your needs.

If purchased directly from Apple, return within 14 days, and re-purchase a Mac with more memory.

16 GB does well for most folks, when combined with the speed of main storage. Folks doing app development, or working extensively with video, performing heavy multitasking, large databases, big apps, and other such tasks, can benefit from more memory.