Need my currency site to auto update

Hi, I have a wordpress website (https://usdtocad.net) whose rate I have to update in a php file daily so need a script to fetch a new currency, pop it in a database, so the site calculator can read that rate instead of one I update manually, and send me an email to let me know it is successful as site must operate 24/7 and it must not change the rate if the update fails. only if the script is successful.

Having said that I get the rate from the live market so not sure what a good, free source would be for the rate so could not give a source. I also have a table with historical rates, if that can autoupdate as well that would be great using values from the database so it runs automatically.

Please only bid if you have experience with this and currency markets as other than the PHP file, I can't offer much guidance.