Firstly, I write a grammar about a language. Secondly, I use \usepackage{tipa} to represent letters LaTeX (TeXmaker) can't represent by itself. If for example I want a ɢ or χ, I use \;G and X respectively in the \textipa{} environment. However if I copy and paste these, the result is X and å. And that's with all letters which I use with the \usepackage{tipa}.
How can I solve this, so that if I copy and paste a text, I get the letters represented in the pdf.

xelatexand an OpenType font that supports IPA characters. See How to use phonetic IPA characters in LaTeX – Alan Munn Jan 16 '16 at 21:29