Six years is a good run. Based on your description, I’d guess you're having hardware as well as software issues. Please be sure your data is backed up/copied elsewhere and verify you can access/restore it. Then if your laptop packs it in, especially the hard drive, you won’t be completely hosed.
Now is a great time to shop as you have more computing options than were available to you when you bought the laptop. If you still need mobility, you could use a tablet or a laptop or possibly a smart phone, depending on your needs.
My only real recommendation in PC/laptop buying is to splurge on more memory than might seem necessary. Memory requirements go up frequently as software versions get upgraded and most of us seem to have the habit of running multiple apps, sometimes dozens of them, at a time. If you use a Microsoft OS, I believe it’s still a good rule of thumb to at least double the minimum specs M$ states for the OS as a start for calculating your needs and then you have to add in each program you typically have open plus allow for documents used by those programs (I’ve seen/used massive Excel, Word, and Access databases opened regularly by users that were a gig or more in size). If you mostly are working on-line, you won’t need as much of course.
Personally, I buy refurbs most of the time and haven’t had issues. It can save money, as long as you can be patient in waiting for one to come available that meets your requirements.