It would take an experienced Blynker just a few minutes to convert your regular Arduino sketch for use with Blynk and in the passed I have posted details of how to do this. But if a Blynker simply provides you with the required sketch you don’t learn anything i.e. why the sketch is laid out how it is etc.
I would urge you to read the Blynkify threads but the basics are that Blynk loop()'s are very different from most basic Arduino loop()'s.
The PushData example at https://github.com/blynkkk/blynk-library/blob/master/examples/GettingStarted/PushData/PushData.ino is a good starting point as it introduces you to timed events which is critical for use with Blynk. You will need to convert the sketch from Ethernet to ESP use and then add in the BH1750, but do it in stages.