I also have only 8 GB of RAM
But why? RAM is cheap! If only my laptop could handle more, I'd add more 
For the reason that I don't feel the need for more than that, everything works flawlessly and in fact I always have a surplus of free memory. In addition, I didn't even check how much max RAM I can add, but I assume that it is more than 8 GB because the laptop is not older than 5 years.
It's a 5 year old laptop which originally belonged to one of my relatives. But yes it's quite old. And trying to fix this might make it worse. So I rather use it how it is, until, I can effort to buy a new laptop or pc. I don't store anything important on this device, so there is nothing to worry about.
Maybe it's a low-quality device or your relatives didn't take good care of it, because I have a laptop that's almost 15 years old and it's still almost as functional as when I bought it (but I paid quite a lot for it) with the note that I installed an SSD and generally cleaned it, but I couldn't find the right RAM, so it stayed at 4 GB.
What I want to say is that there is still a significant difference (or at least there used to be) between premium devices and those of lower quality. Fortunately, I can afford to buy such devices, which, combined with careful handling, can last a very long time.