It's probably the graphics processor unit. From what I can tell in the image the lines are not on top of the HUD items in the game, which is software or hardware failure.
If you haven't restarted the tablet yet, do so now by holding the power button until the option to restart or shutdown pops up. If that didn't fix it, try a factory reset. This will wipe all data on the tablet and restore it to factory settings. Backup all of your important data to your PC then use the factory reset option in settings under "Backup & Reset settings".
Last of all, the problem wasn't fixed by that, than the problem must be hardware rather than software. IF you purchased it within the last year, than it should still be under warranty. Contact Samsung Warranty claim to get your tablet repaired by samsung for free. But if you aren't still covered by warranty, you will have to do it yourself. USe this guide to replace your motherboard: Samsung Galaxy Tab 4 7.0 Motherboard Replacement
(There is no guide for your specific tablet, but this one is a very similar model.)
Hope this helps!
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