Do you agree with this idea? Example: X coin has 100M max supply and there are 50M supply circulating on it's network. They sell 50M+ coins year by year to people who wants to buy it. Imagine a bank gives credit (more money than the bank has) to costumers.
If I understand you well then you
1. Don't understand exchanges and the numbers they display
2. Don't understand banks and their operations
1. Exchanges.
The typical exchange doesn't sell their own money, they only match buyers and sellers' orders.
And since some do day trading, they will sell and buy and sell again and buy again the same and same coins for incredible number of times.
This means big volumes for the exchanges. If you also add the fact that most exchanges inflate their volumes... you'll get to huge numbers.
But no, they won't sell more coins than they have simply because they don't sell coins.
Of course, an exchange could play dirty games with the customers' coins from the cold storage, but that's the sure way to go out of business.
2. Banks do lend more money than they own. It's called fractional reserve banking and it's a common practice (legal too!).