Heart rate is ok and accessible but ideally you want to use power and FTP (functional threshold power) I’m going to do some testing of how accurate the power meter is in the LEVO 2019.I would do some reading up on cycle training and look into heart rate zone training and get a Garmin Edge 500. That way you can monitor and track your effort. It doesn't matter what bike you ride, just the amount of effort you're putting into riding - which a heart rate monitor is a cheap way of monitoring that.
You could also look into getting your V02 max tested if you really want to dive deeper into more accurately tracking your training.