Stuck in Diagnostics mod and trade ins

This is a user-to-user forum, not a way to contact Apple. You were apparently scammed, sold a broken iPhone. Return it for a refund, and contact eBay buyer protection. Apple will only accept working phones for trade-ins.

You can try a forced restart:

• Press and quickly release VOLUME UP

     then

• Press and quickly release VOLUME DOWN

     then

• Hold the SIDE button until an Apple logo appears (15-30 seconds), ignoring "slide to power off" if it appears

The operative word here is QUICKLY; and try it a couple of times, the timing is a little tricky.

and it that doesn’t fix it you can try restoring it to factory settings→Restore your iOS device to factory settings - Apple Support

haiyaaa! please try and force start your device and try again: Force restart iPhone – Apple Support (UK)

Drifter24 wrote:

i did all that it don't work

Then you bought a defective phone. Return it for a refund.

And consider this→The All Too Common SAD Reality of Buying a Used iPad/iPhone