Note to jno...
Give it up, honestly. ;o)
You'll be sucking in damp air forever. Just look out of the window to see the weather we have in this country. Homer's right in his post.
Luca, the best way to dry out is with a little gentle background heat.
It doesn't need to be toasty. You just need to raise the room temperature to something above the point where damp can exist in the air.
Maybe a small electric heater, or one of those oil-filled ones. An electric panel heater, maybe around 200 watts is all that's needed to dry things out within a couple of days, if you leave it on.
The wall looks fine from here. Please take care over re-tiling.
Despite what folk think, tiling in showers is really not a DIY job, unless you are very competent. (Again, ask Homer.)
When all dried out, empty a tube of sanitary silicone around the junction of the walls and the tray.... before you even think of tiling.
The idea is to be as near as possible, completely watertight even without tiles in place. It's a mistake to rely solely on tiling to achieve this. After tiling, finish with a small neat bead of silicone around the junction.
I hope it all goes well. :o)