We have a great big thread called
Does Magic Work in which many people opine at great length and with some heat on this subject - there's been a lot of water under the bridge since then and I don't necessarily feel the same now as I did then, but it should save us going over some of the same contentious ground again.
Actually this sort of question comes up quite a lot as a quick browse through the esoterica section will show.
As you are a complete beginner and we don't know what kind of spell you 'downloaded from the internet' I'd rate your chances of success as pretty slim whatever. I also agree that if the situation is that desperate then the law, or just sticking it out til your ex finally gives up might be a better bet.
The main problem with magic(k), apart from the fact that there's no scientific evidence for it whatever, isn't overdoing it by accident and ending up with a room full of hungry demons or someone dead under a truck, or even that whole 'an ye fuck with another's chi, t'universe will turn round and shit on ye three times three' or however it goes, it's the way that without months and months of very dull exercises to improve visualisation, practice manipulating 'energies', brainwashing yourself that yes, by golly, it does work and building up mechanisms of only going stark raving bonkers when absolutely necessary and finding your way back afterwards, it's all just so many silly words and coloured candals and so on.
That said there are things you could try. Your spell for instance. Go on, have a pop, what do we know, really? Experiment and draw your own conclusions
Or, if someone in your situation approached me for a working for something like this, I'd suggest either a bit of hoodoo, because the 'power' in hoodoo comes largely from the physical substances used, meaning you don't have to be experienced - maybe you want a little
Hotfoot Powder- or sigil magic(k) because it's easy and just about everyone can wank ... sorry, I mean
charge a sigil.
If you want to make sure not to invoke the wrath of the karma-dealing sky parents some traditions insist on, just mangle you desire from 'stay the hell away from me, bitch' to something fluffy like 'may you find a new and fulfilling relationship that allows you to move on and achieve all your wonderful potential' or something - frankly I don't think
my parents would have been fooled by that sort of linguistic wrangling let alone the lord and lady of the universe, but it works for some people
/edit/ - manners - welcome to the board