Help - bathroom tile issues

[Delph123]

We recently moved into a new house, it's about 130 years old
We noticed water leaking in the room directly below the bathtub, and there is visible signs of a leak on the paint work

I have re grouted the tiles several times but the grout above the first layer of tiles directly surrounding the bath kept cracking off on me

Decided to investigate further and took these tiles off, they were only kept in place but the grout and just came away with ease

Behind looks to just be sodden brick or maybe plaster I'm not sure, which is coming away in my hand

What do we do next, a few more tiles above are loose and feel like they would also come away with ease, do we need to pull them all off, how long would the bricks take to dry out and does this have to be done before we do anything else?

Thanks

 

[ree]

You must first, of course, fix the leak or water penetration.

Why not post pics, it will make it so much easier to advise you?