Want to make a calculator like this, where shall I start?

[Mahogany91]

I have an idea for a website, as I want to make myself a tool but also put it on the web to let others use it but am very new to development and have been teaching myself basic code, mainly python through youtube videos. I am not really sure which is the best coding language to learn to achieve what I want to do?  How would I go about making something interactive like this tax calulator but much more thorough, so it can include budgeting, expenditure, and every aspect of a persons finances in a simple tool like this? Any pointers are appreciated, thank you