Idk my password or ID cause I bought it from someone and they didn't tell me it

The someone that you bought the phone from is going to need to provide you with the Apple ID and Password that was used to originally set up the phone so the phone can be erased and set up again.

What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

If they cannot do this, then you need to return the phone for a refund.....because the phone is useless otherwise.

Then the “someone” needs to perform the steps described here:

What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

THEN, you can setup the phone as yours.

Yourgirl_trin229 Said:

"Idk my password or ID cause I bought it from someone and they didn't tell me it"

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Getting Into the Device:

Seems you've been scammed, though a full-assumption, on my part. Always have the setter sign out of iCloud on the device, prior to purchasing it. The seller should have known better.