Why is my monitor running on the PC with significantly more FPS than on the console?

I have the BenQ GL2450H monitor and have not really had any problems with it so far. I mainly use it to play computer games and therefore always had a pretty good impression of him, since most of my games came out fluently and with quite a pretty hue.

Since my graphics card is no longer one of the best, I thought I would get a Playstation 4 Pro for playing future games. To make sure my monitor could handle the performance, I took my brother's old Playstation 4 (and Xbox One S) and connected it to my monitor.

However, connecting and running around in GTA V posed a problem. The game had a fairly low FPS rate and was barely edible. (I had previously played the game on my PC several times, where it ran smoothly and without problems).

My question: Can this really only s.den hardware of the outdated PlayStation 4 and can you run out of problems synonymous of my monitor? Should I worry and buy a new monitor to buy the PS4 Pro?

The ps4 creates with GTA 5 only 20-40 fps

Yes, that's just because the PS4 is only a console is not even at many games even the stable 30 FPS schaffft

So, if I get a PS4 Pro, will you think I'll have a fluid gaming experience?

That should probably make 40-60