How is a programming language written

[Grand Master stickshift]

I hear about the guy who made cpp, and I see game engines with their own personal scripting languages. I wanna know how a programming language is made.

[z05DSL3A]

It's a large field...do a search on Programming language theory

[MikeStgt]

how a programming language is made

Ask Mike Cowlishaw -- https://en.wikipedia.org/wiki/Mike_Cowlishaw -- "inventor" of REXX.
Alternatively have a look at this one, eight commands only and Turing complete, in the description there is even a chapter Language design -- https://en.wikipedia.org/wiki/Brainfuck#Language_design -- extremely fundamental.