I'd like to bring some perspective as someone who comes from a non-programmer background (mainly academic data science with Python and R) and just starting to learn C++.

Bjarne's book seemed to be a comprehensive introduction and I'm currently going through it. I found that adding "using namespace std" at the beginning of the file reduced some of C++'s syntactic overhead that a beginner such as myself has to account for. It allows me to focus on the essential by learning the programming principles, rather than getting stuck on the syntax and having to (annoyingly) repeat std:: every line.

Nevertheless, I think every beginner should know the disadvantages of setting the namespace at the beginning of the file and that no one should use it in production code, but it does its job at keeping things simple if I'm just starting out with C++. There is a reason why Bjarne does this in his book, and I can see why.