My lcd screen are broken should I buy lcd and repair it by myself?

Hi @haryx

Is the phone still usable even with a broken screen or is the screen not working at all?

If still usable, I suggest that if you haven't already done so, that you back up the phone to the cloud or a computer first.

At least by doing this if something goes wrong, you will still have all your data

After that then yes, try replacing the display assembly yourself.

As long as you have the tools to do the work and you're patient and take your time doing the repair, it should be OK.

Here's the ifixit OnePlus 8T Screen Replacement guide that will help.