Create a custom global language file for Magento.

I need you to create a global language file, explain to me where I can later on translate and tell me where to put the file. It only needs to be 1 file for the whole webshop. So for example the file needs to look like this All Product Types","xxxmycustom text This way I can bymyself rewrite everything I want Speed Bonus : 10usd (If you accept and start working immediately on this)