If the graphic performance is deteriorating that is not a driver
problem, it is a hardware problem. Could be a loose or dirty connection with the display panel or graphic card,or a chip that is failing. Impossible to say without testing.
Unless you want to attempt to repair it yourself, then the only advice I can offer in this case is to take it back to where you bought it and have it looked at by a technician.
The correct driver for your card is here; AMD Support Search
It is possible that the manufacturer has modified these drivers
, but not really likely, so it should install.