As recently we have replace our old house rain drain. After digging,
We notice there are several huge crack on the foundation wall. Some of
It even close to an inch. Also there was a ( I shape ) Industry long 25 ft
Long Steel Metal to holding up one of the side of our old house. In
Order hold it up. In that side I found 3 cracks and Now I am thinking
Of add some Metal sheets with bolted each end to improve no more
Unstable to my foundation.
Right now I'll need some advice how to do on this situation. Since we
Have spend a lot already.
Many thanks for your advise in this connection

The problem with any exposed steel buried is in time it will rust and fail.

At this point I would get an engineer to look at the situation there before any band aid is done.

The wall appearers to either have weak PSI in concrete and or no steel rebar in it if at all.

Looks like you are losing the whole corner which could be due to poor footer and or poor soil the footer is setting on. This is not a DIY situation for "patching" There is more here involved then what you think in structural repair.