Hi all!

Hope this is the right place for home repair! I went to Japan for 10 days (yay!) but when I came back home, there was some water infiltration in one of my basement room. The big rainstorm was about 4 days ago, my dad passed by my place on Sunday to water my plants and noticed the water infiltration. They cleaned it up quickly. When I got back, I saw there was some rust poking out of the wall, so I decided to dig a bit. To my amazement, the piece of metal on the corners of wall (Google say "Dry wall corner bead trim" was completely rusted (see pictures) So this might tell me that this isn't the first time that water entered, but maybe the first time was was seen entering.

I decided to remove half of the floorboard (U just landed from a 12 hours plane and that's what i am doing!) It started to smell kind of fishy. I Googled fishy smell, most seems to point toward outlet issues, but it's the floorboard that had the smell (I put my nose on it).

After uncovering half the floorboard, the ones against the wall had white fluffy mold and two of the floorboard had some black mold and was soaked/fragile, it snapped when I lifted it.

I put most of the floorboard I removed in the garage.

From my investigation, the water comes from my slanted garage. the drain wasn't draining fast enough and water infiltrated. As I can see, the "source" of water was the piece of wall that held the closet door. that wall didn't seem to have the black plastic material and thus waster was coming in from there.

So my question is, what should I do from here? I did chip away a bit of the wall to see the damage. Rust was about 15cm (6 inches) high from the floor the the "culprit" wall. I removed about 1 inch of wall from the floor so the wood can "breathe".

I believe the first thing I should do is get a bigger drain grid. My current drain is about 1ftx1ft with 16 one inch holes in it. I will try to find a grid one and do the same for the one inside my garage. I suspect it came from my garage, but could it also come from the foundation outside, where I can't see? Should I also reinforce my garage wall? Is there any way I can do a quick easy repair of the floor? It's my first time working with this scale of renovation. Could I put a piece of plywood on the floor and add those soft floorboard so this becomes a "play room" as a temporary solution (so I can keep on investigating what is the actual source) Thank you all for reading!