Memory Problem with Nano

Projects General Guidance
13

I tried to get rid of the String and use char instead. But I'm confused how to do this whole part with char:

      String readString = BTserial.readString();
      int firstClosingBracket = readString.indexOf('<');
      int secondClosingBracket = readString.indexOf('>', firstClosingBracket + 1);
      String readString1 = readString.substring(firstClosingBracket + 1, secondClosingBracket);
      if (readString1.length() > 17) { readString1.remove(17); }