Acer Aspire E11 E3 112 C455 memory issues

What kind of machine is this that ive just bought?

Its speed slows up bit by bit over the course of a hour or so util it just crawls along. Switching it off and restarting it speeds it up, but just for an hour or so and we are back to the crawl again.

Today though, while I was stuck on the phone, it came to a dead stop. "There isn't enough memory to perform this task" and tells me to close down all of the programs that I have open - namely Firefox, VLC media player (playing a radio programme) and a copying that I am carrying out to an external drive).

However, I can't close anything as the mouse pointer has frozen in position. And Control-Alt-Del is doing nothing, presumably because there isn't enough memory to work it. If I simply switch off the laptop, I'll presumably foul the copying process, lose data and maybe corrupt the disk (this has happened before).

But what kind of machine is that I've bought, that doesn't have enough memory to carry out the most simple functions?