Not sure from the photo what faint lines you mean.

Suggest you use one of the many downloadable bed levelling tests and check the overal bed for high or low spots. Once you have it level try redoing the test and vary the 'Z' offset in 0.01 increments until you get an acceptable first layer thickness.

A 'Z' offset of 0.5 is more than twice the normal 0.2 layer height and you are virtually printing in mid air.
Also give the bed a good clean with some IPA and then preheat before initial nozzle height adjustment prior to bed level test.
A slower speed around 50% for first layer might help.