How to disconnect negative battery cable on Hyundai sonata 2017 (base)?

The negative battery cable is connected to the chassis or engine block, and the battery itself usually labels the negative terminal with a minus. Since all that is so hard for you, I strongly suggest you ask a neighbor to introduce you to basic tools and their proper use. I bet you can find a youtube that shows this being done. It shouldn't be hard for you to find that. You don't really need to disconnect the battery just to change a headlight bulb. Doing that might leave you with other problems, such as the anti-theft locking up the stereo or even immobilizing the car.

You don't need to disconnect a battery to put a new headlight bulb in. if you can't figure out how to disconnect a battery I highly recommend you close the hood before you get hurt jojo.

If the key is off and the light switch is in the off position, there's no power going to the headlights and no need to disconnect the battery cable. In the future, if you ever need to jump start another vehicle OR your vehicle needs a jump start, make sure that everything is turned off first.....headlights, A/C, radio, wipers, etc.

Hmm that is very complicated. You will probably need a size 12 metric spanner and undo the nut on the negative terminal

Why would you need to disconnect a battery cable to deal with a headlight? Take the fuse out that handles that headlight. Check the fuse while you're at it.