Well if the phone was sold in the UK the Sale of Goods Act would cover it: it clearly isn't fit for the intended purpose, and as such you would be entitled to a full refund.
There may not be much you can do to improve it. This particular one may be a lemon, or they could all be like this. Getting reliable specs for devices like this can be tricky (vendors are not always either reliable or consistent, and nobody else has any information), but from what I can see this is very much a 2013 device spec-wise. I guess you've tried a factory reset? I'd be surprised if this device has any customer support, so there's probably not much else you can do - maybe disable some unnecessary included apps, but apps force closing before loading sounds like a more serious problem than just lack of resources.
I'm not going to suggest rooting it. Although in principle if there is a solution and you knew what it was root might help you implement it, it won't help in itself. And while some dodgy tool might be able to root a device like this, there's no guarantee that tool won't add to your problems, as well as possibly giving the vendor an excuse to refuse a refund (if there's any possibility of that in the first place).
