Alright, based on your newer replies, it seems like problems arose on their own, not because of any modifications or disassembles you've done yourself. This is going to make the problem harder to diagnose, because we can't trace a probable cause to any direct action you've taken or witnessed.

I was looking for a guide to refer you to, but I'm not finding one easily. I'm aware that a language barrier could be an issue, so I'll try to state this as plainly as I can:

When you disassemble the Game Boy Color, you will find that the internals are a single circuit board, and that the display is attached by means of a ribbon cable looping over the top of the circuit board and connecting to a locking header on the other side of the board. Fortunately, I find this a lot easier to work with than the ribbon cable found in the first game boy model.

To disconnect and reconnect the ribbon cable, you must open two brown tabs on the header. All of these parts are fairly delicate, so be gentle. Do this by catching the edge of each one with your fingernail and pulling it up towards the top edge of the circuit board. You will feel a very slight click as the locking tabs disengage. When they are disengaged, the ribbon cable can be readily removed, and just as easily reinserted to reconnect by pushing each tab back into place.

If the ribbon cable has no apparent damage and you can connect it properly, then I am at a loss for what else could be a ready cause of this problem from your description. The purpose of your disassembling the Game Boy at this point would have just been to make sure that the ribbon cable is intact, undamaged, and properly connected. Double check these things once or twice and see if the screen works when you reassemble the game boy.

I hope this was helpful, and good luck!

how do I fix the ribbon cable?

if you heard the sound, its booting correctly, so its definitely the screen, probably the ribbon cable

hmmm i trying to disassembled my gbc now

probably a ribbon cable thing then. not sure what to tell you.

when last im turn on , display not appear but sound default " Tling " still heard
I'm confused because problem is in the LSDJ or Gameboy ?  How to disassembled gbc ?

This is going to sound like a stupid suggestion, but make sure you reconnected the ribbon cable to the display when you reassembled the Game Boy Color. I've forgotten to do this before.

This is, of course, assuming that this problem began after you disassembled it or modified it. You didn't really state the conditions under which the problem arose.

contrast knob? ribbon cable ripped? gameboy's out of power? it's just fucked? couldn't tell you for sure unless you described it a bit better.

Help me guys , was when I turn on, suddenly the display does not appear, why? whether its gemboy or LSDJ  problematic?