Is it normal or resolutions of my laptop/pc I used to affect the performance? Well, I still could scroll it down by using the keyboard just for the first time I was thought I could not do it since there's no scroll bar inside.
It probably has to do with your laptop's screen resolution. Some css tricks may solve the problem for you, I'll see what I can do in that matter. In the meanwhile, you can scroll like you said by using keyboard arrows.
2) When the user clicks anywhere outside of the modal, close it (Source:
w3schools)
sometimes there is a difficulty to close a pop-up especially when the post is long
If you press the Escape key on your keyboard, the pop up will close. Having it close also when the user clicks outside of the pop up is a good suggestion idea for future versions.
1) Display content align like the original post rather than center it
Noted.