In the meantime, I have a question related to programming. I am creating this website about countries and I am wondering what can I do to have an up-to-date population of a certain country. Do you have any idea where I can start or what to do? Your help would be appreciated!
An API is probably what you want. There are several with information you are looking for. One option might be Countries API on RapidAPI. The free option will give you country name, capital, population, ISO codes, and some UN geocode information. There are also paid options with much more data.
There is a free Countries API, you can fetch the data about the countries that you want to list, including ist population;
For example: fetch => https://restcountries.com/v2/name/usa Will return a object containing many info about the country including: