Your computer repair shop has already ascertained that the problem is in the screen itself and not in the computer as a whole by projecting the display on a second screen. So this means it is a hardware issue.
a) The cable connecting your screen and the unit has broken or become lose.
If it is broken, then it will have to be replaced (not too expensive, within Rs2000)
If it is just loose, then it can be fixed again properly at bare minimum charge.
b) There is a damage in the screen itself
This would require a replacement of the entire display panel, which you should get done only via the official Acer customer care service center.
You can call their toll free customer care number 1800-11-6677 to get step by step guidance to either determine the exact cause yourself or they can provide you information regarding the nearest official service center.
If your laptop is not under warranty, the replacement of a touchscreen can at times cost over Rs10,000. An actual figure can only be given to you by the customer care people. In case you are told that replacement of screen would be required, you can ask them about buying a full cover warranty.
I have done that once, with Dell laptop though. I bought a full cover warranty worth Rs7000 and got repairs done under this warranty on site (at my home) worth almost Rs30,000.