How do I fix no network and function issues on iPhone X?

You can wait as long as you like.

The fact is Apple won't touch it now that it's been tampered with and unapproved parts have been installed.

Either find a 3rd party shop and ask them if they can help you or go buy a phone that works.

but I changed the previous display carefully and everything was fine.

Irrelevant, you damaged your phone and Apple will not work on it.

You could try a third party repair shop and see if they will work on it but if you damaged the motherboard, they can't fix it.

Then your going to be waiting forever. Here are the facts -

• You broke your phone whether you want to believe it or not.

• You aren't going to get "a more adequate answer".

• Apple will not touch any phone that has been tampered with by unauthorized personel.

• You might be able to have it looked at by a third party repair shop but don't expect them to be able to fix it.

• it's time to buy a new phone.

Was the display replaced at an Apple Store or Authorized Apple Service Center?

• Yes. Return there and seek assistance.
• No. Apple will no longer assist you with this iPhone.

lorrynglovez wrote:

everything worked like that when I changed it and then after a while it disappeared/

I have already changed the display at least 40 times and not only for myself and everything was fine

Doesn't matter. You borked the job. Apple won't touch it.

End of discussion.

You can argue all you want, it won't change the fact that you somehow damaged the phone.