No matter how sharp a knife is initially, after some use it needs sharpening, something you can achieve with a sharpener, whetstone, or honing rod.
You can determine if your knife cuts well with an easy test using the knife and a sheet of paper. A sharp knife can easily and cleanly cut a sheet of paper. Conversely, a knife that needs sharpening will struggle and the 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's edge and to maintain its sharpness.