2 LAN cables connected, slower?

So hello first, I have a long cable from the Wi-Fi box connected to my Playstation 4 and 1 on my laptop.

Now the question: can it be (we have only bad Wi-Fi) that if I synonymous if for example the laptop is off and I play Playstation 4 that the Internet is slower then because 2 devices are connected? (As I said laptop is off)

When he is out, everything should be alright

No, it makes no difference. Only if you use both at the same time, of course, it affects the speed.