[denNorske]

A good place to start would be here:
https://sampwiki.blast.hk/wiki/Format
https://sampwiki.blast.hk/wiki/Strcat

As it was told above, your code "format" the string every time (https://sampwiki.blast.hk/wiki/Format) which means the string is being deleted and replaced with something new.

If you use strcat (https://sampwiki.blast.hk/wiki/strcat) you can append new parts every time.

Everything you need to know is explained on the Wiki