LIghtroom classic develop module showing small photo window

I changed the DPI settings in Lightroom. I read a thread here (can't find it again) basically instructing to apply high DPI scaling override. 

• find the LrC exe (or even the shortcut to LrC)
• right click, then Properties
• go to Compatibility tab > Change high DPI settings
• Override high DPI scaling behaviour > [Application, System, System Enhanced]

Originally, I used the System Enhanced option to fix scaling problems between my 4k laptop screen and my FHD 2nd monitor , but that's when the issue on small photo window arose. So now I choose the Application option, which solved the problem, but Im back to my original scaling issue. 

Thank you for your reply. It didnt help. But for some reason, it disappeared when I changed the high DPI settings. My problem now is that the texts are too small in my laptop screen (4k) but too big in my secondary monitor (FHD only). I know there is a thread to resolve this, I will try that first. But Im afraid that the same problem will come back once I adjusted the DPI settings. I will update this thread on what will be the result.