In a string to format (mostly to replace chars with different symbols for rendering test on UI), I have to detect % and then skip all chars util first space from this % char
You can get that pretty easily, just grab the index if the first percent sign and then leverage that index to find the first space from there:
var start = myString.IndexOf("%");
var spaceIndex = myString.IndexOf(" ", start)
of course the value of myString is the string you represented in your question.