How to remove character in C#

Sitecore's solution is correct. It looks like you are getting escape characters in your strings. If you want to exclude all characters that are not alphanumeric or ':' you can use the Regex class like this

string testString = "\"status\":\"ok\"";
var regex = new Regex("[^a-zA-Z0-9 :]");
string cleanedString = regex.Replace(testString, "");
Console.WriteLine(cleanedString);
Console.ReadLine();

What it is doing is matching all characters that are not a-z,A-Z,0-9 or : and replacing each with an empty string.

You need to understand escape chars and literals in C#.
Escaping in C#: characters, strings, string formats, keywords, identifiers[^]

Depending on where a string come from, user input, external file, literal in code, literal in executable, the end result is not the same.
if you have "\"status\":\"ok\"" in source code, you will have "status":"ok" in executable.

Solution is probably what you need to solve this problem.