[Solved] Jeep Grand Cherokee (1999 - 2000) - How to connect another radio?

Hello, I wanted to connect another radio to the Jeep Grand Cherokee (1999 - 2004).
Such:

https://centrumaudio.pl/caliber-dvd/74-caliber-rmd574bt-radio-1din-7-usb-sd-dotyk-8gb.html

It supposedly has a steering wheel control and I wanted to use it, it has two boxes, one under the back seat - I don't know what it is ... and there is a power boost under the front passenger seat. Chincze are between the radio pocket and the seat.
I plugged it in and it doesn't work, can't hear a voice. I wanted to "disarm" it so that the radio signal from the radio would go straight to the loudspeakers, but I decided to describe my problem here, maybe someone will tell me clearly what to connect to.
Someone has already tried to connect something in it but gave up.

I am asking for some small diagrams to illustrate it somehow.

Best regards, Damiano.

Upload a photo of the fuse box which is under the hood. I used to deal with a similar problem. It was necessary to make a small modification, namely to control the relay that activates the amplifier so that it turns on when the ignition is turned, at least I did it. The radio controlled the amplifier with a high audio level.

This is under the rear seat.
And these are some TV amplifiers for receiving programs, but this will not be anymore because we will not receive programs ... and there is an audio terminal under this seat, such a small box (that's why I write audio because I took it apart ...) that's why I'm surprised what it is here under this rear seat it's big.



In the photo, this small box is not visible because I had it on my desk, but the two-row plug as shown in the picture and 4 chinchas are also on the radio pocket, but the beam is not there, it is the original plug from the speakers.



Added after 1 [hours] 11 [minutes]:

ao are a few photos of the car:



under the steering wheel

And this is under the hood:




Plugs from the radio pocket (I suppose what went to the speakers comes from this box under the front seat)



And this is this little box: (I unscrewed this power amplifier)



And this is that big box in the back seat:



And this is a diagram of this radio that I want to connect - only for illustration for those interested:


If I can't handle it here, I will take it all out and plug it in without it all because I won't get it.

Added after 4 [minutes]:

Please do not look at these cubes because it is only to move for now, then cool connectors will do ...

The one under the front seat is not the original amplifier, the factory amplifier sits under the rear seat. There are diagrams for this car in the "download" section, there is also audio. The original amplifier receives the signal from the radio's speaker outputs, which is additionally amplified and then fed to the speakers.

I also came to it by deduction and threw it out, now I will only change the dice to such a universal iso - thank you for your interest in the topic.

And tell me, my friend, what's the antenna thing like?

Because waves are escaping from the radio in which direction the antenna installation should go - there is the original harness of the socket, power supply and loudspeakers, I left the adapter and took this additional amplifier from under the front seat.
Everything works as it should, but I unplugged the TV antenna because there were some amplifiers for the TV that is on the ceiling, I want to connect it to this radio as an additional monitor for this radio, but so far it does not display anything.

Radio's fault that the waves are escaping, we made a new antenna, everything sounds on the original amplifier and speakers, thank you observers for your attention - greetings Damiano
I plugged the ISO plugs - the rectangular ones that fit many receivers - "gra i bucy"