In my experience, the most effective way to decrease boot time without upgrading is to go into Settings > Apps > Startup, and to disable some programs you don't need immediately at startup. Your computer is from 2016 so I imagine you will have accumulated quite a lot of programs you don't need in addition to some OEM bloatware. To be honest though, what I would do in your case would be to buy a new SSD for your computer. SSD technology becomes obsolete pretty quickly, and drives from today could be multiple times faster than drives from 2016. This is the SSD I recommend: https://www.amazon.com/Crucial-500GB-NAND-NVMe-PCIe/dp/B07J2WBKXF. It is confirmed to work on your 17 R3. If you wish, you can choose to get the 1tb or 2tb variant, but considering you haven't even used all the storage on the 256gb SSD with 4 years' worth of programs, 500gb will probably be more than enough. Best of luck and stay safe!