Being a 7 year old monitor. No telling how many operating "hours" are on it.
* Open the OSD (On Screen Display) -Other Settings
* Choose Factory Reset -Reset All Settings (page 29)
* Then post some pictures of the standalone Built-in Diagnostics screens (page 39)
Looks like you have some image retention and also some yogore/mura smearing defect. You can try to run the LCD Conditioning (page 30). But it may not help this old monitor. Might be time to replace it.
Don't know what you mean by "matrix". I think you mean the panel itself. Dell does not repair monitors, sell monitor components, or have disassembly documentation. Your only option is to look for spare parts on eBay or craigslist.