No matter how sharp a knife is initially, after some use it needs sharpening, which you can achieve with a sharpener, whetstone, or honing rod.
You can tell if your knife cuts well with an easy test using the knife and a piece of paper. A sharp knife can easily and cleanly cut a piece of paper. In contrast, a knife that needs sharpening will struggle and its cut will be jagged.
It is also recommended to occasionally have your knives sharpened by a professional to repair any potential damage to the blade edge and to maintain sharpness.