See the string function calls here: https://docs.mendix.com/refguide/string-function-calls#1-introduction
Use find to get the position of the dot and use substring to cut the string apart. See also the video in the introduction.
Regards,
Ronald
You can use string functions like this. First find the index of delimeter, then get substring from start to delimeter, or from the delimeter to the end.
substring($string, 0, find($string, '.'))
OR
substring($string, find($string, '.'), length($string)-1)
If you have advanced usage, you can use the string utils functions from the community commons function library