If you are using the Shavian alphabet, what language are you speaking or writing?

Shavian Alphabet is a phonetic way to write and pronounce the Latin alphabet. It was created by Kingsley Read and funded by Bernard Shaw.

https://www.shavian.info

You would be speaking English!

George Bernard Shaw created a competition for a new English alphabet with at least 40 letters. His motivation was to ease and advance communication by providing new characters for specific sounds, thus erasing the many contradictions and anomalies in English spelling (think of the pronunciations of through, though, bough, and cough, for example).

The 48 characters in the chosen entry are written with just one stroke, similar to shorthand, ostensibly making it easier to write and learn.

There are some examples here. It is also known as The Shaw Alphabet.

https://www.atlasobscura.com/articles/puzzles-shavian-language