My bearings or wheels don’t spin well

Bearings used in skateboards are often rated by something called the ABEC standard. Most commonly, ABEC 3 to 9 bearings are used, and higher numbers indicate higher precision. Intuitively, higher precision may seem better, but extremely high-precision bearings like ABEC 9 are originally designed for delicate machinery. Even a small amount of dirt or a slight impact can quickly reduce their precision. The important point is that even if their precision drops significantly, they still perform more than well enough for skateboarding. Also, bearings will eventually wear out or break. Rather than focusing on high ABEC ratings and buying expensive ones, it is often more practical to treat them as consumables and choose reasonably priced options.