I have some pretty common knives at home that I use for cutting vegetables, fish, meat and everything else that needs cutting. I don't have specific knives for specific kinds of food but rather use all knives for everything depending on what is quickly available.
Some the knives have become dull over time. I can still cut stuff with them but food that's a little bit more squishy like tomatoes can't be as precisely cut as before.
The knives were bought in a local supermarket and are just kitchen knives, nothing expensive or special.
How can I most effectively sharpen these knives? Does it even make sense to sharpen them again or should I just buy new ones? If I were to use a any additional equipment (whetstones, etc.), how do I best use them from a technical point of view (sharpening in a certain degree, etc.)?