BEST app for tracking & fertility??

So my husband and I just started ttc this month and I want to know what app is the best? They're all saying cycle day 7 but the fertile days are all different. 🙄 how do I know which one is the most accurate? I know for a fact glow never gets my period prediction right like iP does. But does that mean the fertile days are wrong. SO CONFUSED!! SOS!! I don't want to waste our time & energy 😂