Connecting Decoder, PS4 & LG 42pc3ra TV via 1 HDMI: Splitters, Adapters & Input Lag Concerns

Hey,
I have an old LG 42pc3ra TV and for this the decoder from the digital polsat HD300 are connected by an HDMI cable. In the near future I plan to buy a PS4, but I only have one hdmi input and now my question is if there are any "hdmi adapters, splitters", or maybe you have some thought on connecting the decoder to another input but without losing quality.
I still have a question, if I don't have game mode on my TV, it is suitable for the console? I read about some input lag and now I'm not sure.
I do not know these matters, so I prefer to seek your advice.

Are you determined on PS4? Because Xbox One has in addition to the HDMI output also an HDMI input and the decoder can be connected through the console.
Otherwise, only an HDMI switch, preferably one with a remote control.

Yes, I am determined for PS4 consoles. I found something like "http://allegro.pl/switch-rozdzielacz-hdmi-full-hd-3-in-1-out-pilot-i6600000717.html#" was this a good idea? The attachment is also different.
And so coming back my TV fits this console or rather let it go with the console. I read about some input lag and game mode and in my settings it was missing.

domel55 wrote:

I found something like this

Buy it - more certain that it will work and has 4K (for now you won't use it with your TV):
http://www.dipol.com.pl/switch_hdmi_3x1_signal_4k_x_2k_60_hz_hdmi_2_0_H3132.htm
Or the cheaper version without 4K:
http://www.dipol.com.pl/switch_signal_hdmi_3x1_H3131.htm

Save toys from Allegro.