Should I invest the money I don't need immediately and only withdraw it next year when I need it for living expenses or should I simply leave it in my current account?
This might come as a bit of a surprise, but your money is already invested.
We talk of investment vehicles. An investment vehicle is basically a place where you can put money and have it either earn a return, or be able to get it back later, or both. (The neither case is generally called "spending".) There are also investment classes which are things like cash, stocks, bonds, precious metals, etc.: different things that you can buy within an investment vehicle.
You currently have the money in a bank account. Bank accounts currently earn very low interest rates, but they are also very liquid and very secure (in the sense of being certain that you will get the principal back).
Now, when you talk about "investing the money", you are probably thinking of moving it from where it is currently sitting earning next to no return, to somewhere it can earn a somewhat higher return. And that's fine, but you should keep in mind that you aren't really investing it in that case, only moving it.
The key to deciding about an asset allocation (how much of your money to put into what investment classes) is your investment horizon. The investment horizon is simply for how long you plan on letting the money remain where you put it.
For money that you do not expect to touch for more than five years, common advice is to put it in the stock market. This is simply because in the long term, historically, the stock market has outperformed most other investment classes when looking at return versus risk (volatility).
However, money that you expect to need sooner than that is often recommended against putting it in the stock market. The reason for this is that the stock market is volatile -- the value of your investment can fluctuate, and there's always the risk that it will be down when you need the money. If you don't need the money within several years, you can ride that out; but if you need the money within the next year, you might not have time to ride out the dip in the stock market!
So, for money that you are going to need soon, you should be looking for less volatile investment classes. Bonds are generally less volatile than stocks, with government bonds generally being less volatile than corporate bonds. Bank accounts are even less volatile, coming in at practically zero volatility, but also have much lower expected rates of return.
For the money that you need within a year, I would recommend against any volatile investment class. In other words, you might take whichever part you don't need within a year and put in bonds (except for what you don't foresee needing within the next half decade or more, which you can put in stocks), then put the remainder in a simple high-yield deposit-insured savings account. It won't earn much, but you will be basically guaranteed that the money will still be there when you want it in a year.
For the money you put into bonds and stocks, find low-cost index mutual funds or exchange-traded funds to do so. You cannot predict the future rate of return of any investment, but you can predict the cost of the investment with a high degree of accuracy. Hence, for any given investment class, strive to minimize cost, as doing so is likely to lead to better return on investment over time. It's extremely rare to find higher-cost alternatives that are actually worth it in the long term.