[alerts04]

I would like to understand the general concepts behind C language and how to oversee, for example, website functionality, payments (Crypto + FIAT) and security.

Is there any good guides on where to start?

Any help is much appreciated

[Pοιsonlεaf]

Assuming you don't know anything yet I would say start with the basics, always start with the basics.
https://www.w3schools.com/c/c_intro.php

[alerts04]

Thanks for such a quick reply, I am looking for anonymity tips and how to have a 'hidden online presence'.

I have read a few things about burner emails, monero, proton, vpns but there's so much information and am unsure about how anonymous this stuff all really is.

[Pοιsonlεaf]

What happened to "understanding the general concepts behind C language"
Already gave up? You're looking for Opsec btw. Go see the Opsec section here.