First of all, whether it is possible to repair your device would depend on the amount of water that fell into your laptop. It also depends on your overall budget.
Now you have not explained clearly what 'not working properly' means. So if the issue is that your device is not switching on, the problem could be a defective motherboard that was shorted out. If this is the case, you should understand that a faulty motherboard is expensive to repair. So be prepared to spend some cash.
If your computer is turning on but the keyboards or the touchpad is not working as it should, then the damage might only be limited to these components. These components are easily replaceable and they don't cost a lot, at least when compared to a motherboard.
Most probably the reason for this should be your video or graphics card or it could be a problem associated with your memory. The problem could also be due to the accumulation of dust in your system. Or it could be overheating because of a problem with the internal fan.
1. There might be a lot of viruses or spyware that might have installed themselves on your computer without your knowledge. If this is try installing anti-virus software and that problem could be resolved. 2. Overheating could also be the reason. It could be caused by multiple programs running in the background. If that is the case close those that are not needed and try again. Overheating could also be due to dust getting into your system. If so slowly clean with a small brush. It could also be a faulty fan that's causing it. If that is the case contact a PC repair shop. 3. Your laptop might not have enough memory to meet your usage requirement causing it to slow down.