lines appeared my samsung tab s 6

[Members_xKotwE6]

hi after just using my tablet for only a week these lines starting to appear, like is this a common fault and how can this be fixed. Like i purchased the device from a seller on ebay would it be best to return the item or get fixed if it is repairable 

[Newtos8p]

If, you can return the item it will be the best option for you. But that look like a demage screen. Either way it is pressed hard on the screen or been dropped on floor.

[Glenntech]

It maybe worth trying to factory reset the device in case you have an app or Theme affecting the device.
Otherwise that looks like it will need a screen replacement.
Get back to the seller and see if you can return the device if you can't resolve it by a reset.
If the seller is a retailer, then you should have a right to return the item. But if its a private seller, you may have to go through other means.
But if they can prove it was working OK, and it's got damaged subsequently. Not sure where you'd stand there. Particularly if it's second hand.
Hopefully you can resolve this issue soon