Please answer it. Thanks :)
First off, a continuous thick bead of silicone caulk needs to be between the bottom threshold and the floor [or shower pan]. Since it is leaking between the bottom of the door and the top of the threshold, here is the solution. The bottom of the door should have a drip edge that hangs down at an angle so the water that runs down the inside of the door falls into the shower pan instead of wicking under the door. It looks more like an upside down Y rather than a T shape. Most quality doors have this already installed, but your friend might have had to install it and forgot. Most are either attached with 2-faced tape or screws and caulking. As far as a rubber seal, there is sometimes a magnetic strip if the door is a swing model. I think there is an issue with the drip edge missing in your case.
5 Years is the expected life of a smoke detector, they need to be cleaned on a regular basis, the battery should be replaced every 6 months. Write the date on the battery when you install them.
Vacuum out the detector. Sound like dust or grease is on the contact points
