css - background image doesn't work on safari -

i new programming , made first website friend. www.goalstars.be apparently background image of landingspage doesn't work tried solutions posted here nothing seems fix it. runnning head in wall. think made huge mistake somewhere. can me. in advance

this css code use header

header {      background-image: url('img/landing.jpg');     background-repeat: no-repeat;     background-size: cover;     background-position: center;     height: 100vh;     background-attachment: fixed;     border-bottom: solid 1px #00ab1c;     z-index: -1; }  

i had same problem safari, removed negative z-index , worked me