No you won't have the savings to do as you want with. You have a €255k mortgage today and €1k in savings. If you pay the €1k off the mortgage, you will have a mortgage of €254k.
Would you be better off buying shares with the €1k? Probably. Over the next 10 years or so, the stockmarket returns after tax should exceed the mortgage rate after tax. But there is a risk that it might not and you would be worse off.
It depends on your overall financial positon. Is the mortgage of €255k uncomfortably high in relation to your earnings and in relation to the value of your home. If so, reducing your mortgage is the best option.
If you have a comfortable mortgage and can handle the downside of the stockmarket returns being lower than the mortgage rate, then you should buy shares.
Brendan