If you are confident enough, you can open the laptop up, and replace the hard drive with a solid state drive. You would want a 2.5" sata size. You will just want to make sure any important stuff is backed up, and you will need to reinstall windows. This might actually be beneficial to get rid of bloat that manufacturers install on those machines as well. It would also be a good time to clean dus from the fan/heat sink, and add more ram(short term memory for more multitasking)if necessary. Most people want 16gb in the modern day. You will have to look at your system information to figure out the kind and amount. The ram will be the SODIMM form factor.

Yeah probably best to go used. Try for at least 4 cores, 16gb ram, and an ssd for the boot drive. Also good to clean dust out when you get it.

A 500gb ssd is like $25 USD. You can keep the hard drive for general storage, but don’t put the os or commonly used programs on it.