We require help with fine tuning signal processing code in C++ to improve the feature extraction

I have signal processing code which extracts features from ECG signals. It requires good knowledge of Signals ( mainly ECG ) to understand the code. Code is working fine, someone who has good knowledge on signal processing can help me to increase the accuracy This code is feature extraction part of Machine learning model. If you improve the signal processing ( feature extraction ) it will increase the model accuracy. Goal is to fine tune c++ signal processing code, test it with the test data I have and get accuracy as I explain.