See the string function calls documentation here: https://docs.mendix.com/refguide/string-function-calls#find
Use the find option to find the first occurence and use the substring to cut up the string.
Hope this helps,
To build on what Ronald said, you could do the function combination like so:
to find all the characters after the first >>. To remove all the characters after the second >>, you could use
so that you return all the characters between index 0 and the index of the second >>
I built a small test workflow that produces the results you want. Values are below the Actions
Hope that helps,