The amount changes all the time, and depends on what you define “money” as.
Almost every country (every one on the WTO) publishes monthly volumes. Here’s the one for the US if you consider that money is cash and the contents of all the bank accounts:
https://fred.stlouisfed.org/series/M1SL
That “M1” is a standard definition, that is easy to search for any country.
If you start to add things like credit card balances and government papers that can be used in most large transaction, you arrive at the other definitions. There’s a wiki page for them:
https://en.wikipedia.org/wiki/Money_supply
The M1 to M3 set is an international standard, but many countries add other definitions to their publications.
EDIT:
And of course, I didn’t tell how the amount changes.
Each kind of money changes by its own particular process, that is actually quite obvious once you think of money that way.
Cash is printed by the government, and destroyed mostly by it too (but some times by accident). It’s a form of government debit.
Bank deposits are created when banks make loans (that is, they get somebody’s money and give to another person, but still keeping the first person’s money on their account), and destroyed when the loan id paid back.
Credit card debit is created when people buy stuff on credit, and destroyed when they pay it back.
And so on.






Some (many? most? IDK) gold sellers are scammers. They will sell you overvalued stuff and insist it’s extra-valuable because of some feature they made up. They are the ones being loud on the web and making you hear about it all the time. So, if you hear an ad, and buy gold, you’ve probably fallen for a scam.
But investing in gold by itself is just like any other commodity. And just to say, the rule on that last phrase is valid for almost everything (it’s absolutely valid for stocks and investment funds).