I am new to macroeconomics and I had some questions about GDP when we say that it does not take into account intermediate goods. Therefore, a company X that only sells car parts to car brands like Mercedes for example, will not "directly" impact GDP at all right ? The part of GDP that X produces is entirely contained in the GDP of the companies that sell the final good (car), right ? What about a sponge that a cleaner buys to clean someone's house. Is it an final good or an intermediate good that will be counted on the salary of the cleaner ?
Also, I dont understand why GDP doesn't take used goods into account. If I buy a computer for 100$ and resell it for 1000\$, there is a huge profit that does not appear in GDP which makes me feel uncomfortable with this notion. What if I own a resell company that buys used goods and resell them ? It does not contribute to GDP at all then ?