Retrofitting FI switches, older electronics

Hello,

as some of you have already read, I am currently renovating one of my 1.5-room apartments. Unfortunately, there is no RCD in this apartment. Of course, I would like to retrofit one.

Now, I don't really know much about electronics and before I call an electrician, I wanted to ask you for advice. As you can see in the photos, there are already sockets with green-yellow protective conductor (bathroom, kitchen, partly living room), but also sockets without green-yellow protective conductor (also living room).

The photo with the black/red/grey cable is a switch.

Now the crucial question: Can an RCD be retrofitted there without having to break open all the walls? If a green-yellow protective conductor were installed everywhere, I would have said yes – at least from what I have read. With a "neutraling" (i.e. without), no. But how does it look here? I will not tear open the entire walls. If retrofitting is not possible, I would probably install RCD sockets in the bathroom and possibly the kitchen.

Regards

Now I don't really know anything about electronics and before I get an electrician, I wanted to ask you for advice.

For that reason, only hire the electrician and nothing else. He can tell you on site exactly what is possible and what is not. We can only speculate here based on the pictures.

For that reason, only hire the electrician and nothing else. He can tell you exactly on site what is possible and what is not. We can only speculate here based on the pictures.

I will do that too. I just hoped for an assessment or opinion in advance.

If already, then really. Two RCDs are required, you only have one and it trips, you are literally left in the dark. Basically, measurements have to be taken first, otherwise nothing works at all.

At least two circuits would need to be combined in the distribution to accommodate the RCD (four modular units). Everything else can hardly be assessed based on the pictures.

In the distribution, at least two circuits would have to be combined to accommodate the RCD (four modular units). Everything else can hardly be assessed based on the pictures.

What exactly does that mean?