I can’t transfer my data from an Android to an iPhone 6s

First try this --> Move from Android to iPhone, iPad, or iPod touch - Apple ...

If that fails or you do not want to attempt or have already set up your device. then...

You can still transfer these data.

• Photos & Videos --> Upload to iCloud Photos using the same Apple ID that you have used on your iPhone. After upload, enable iCloud Photos on your iPhone. That's it.
• Contacts --> Contacts are not stored on an iPhone nor on SIM, they are synced to  Google, iCloud, AOL, Exchange, Outlook, Yahoo or any Other. Upload all your contacts to any of the above email client server.
• Any Specific Files --> Upload to Cloud Drives (iCloud Drive, Google Drive, OneDrive, DropBox, Flickr, box, AmazonDrive, Adobe Creative Cloud and Use Files app on iPhone
• Apps --> In any way they have to be re-downloaded using the App Store.