Buzzing Noise from speaker when connected

Hello,

I have attempted to repair a switch lite, I have exchanged the battery, the ribbon cable to the motherboard, the lcd screen, touch screen digitizer, and the volume and power flex ribbon cable. after those repairs, I was able to hear sound from the console but the screen wasn't showing anything.

havent attempted for quite a while now, and now when i plug in charger, the fan isnt working, it gets hot around the usb c plug and from teh speakers, a buzzing noise occurs when i have it charging and "turned on"

Not too sure what i should do next.

How do I get rid of that noise and overheating?

and How do i get images to pop up when turned on?

Any suggestions will do.