Didn't the repairer notice that there was a problem before handing it back to you?
Seems very strange that they just hand it back without telling you that there may be another problem and that it wasn't the screen. Not very professional on their part.
Unfortunately I don't know what you can do in this situation unless the repairer gave some sort of guarantee on their repair.
They might say that they did replace the screen OK if that's all they were asked to do and not to repair the phone to a proper working condition. They should have told you about the chip problem and asked if you wanted to proceed further, not just hand it back and wait for you to get back to them about it.
Did the repairer give you an estimate of how much it would cost to repair it?
At best perhaps if you want the phone in a workable condition is to go to a more reputable professional repairer and ask for a quote to fix it. Staying with the first repairer wouldn’t be a good idea
They might say that given the age of the phone it is more economically viable to get a new one as you may be spending more on getting it fixed than what it is worth.
Whatever you decide, even though the phone may be hard to use in its present state, make a backup of your data from the phone to a computer or the cloud, using the phone's backup feature. At least that way you got a copy of your data if the phone fails further or the repair causes a loss of data for some reason