RUST!! Help

Hi, Ive found this rust next to the rear beam mounts and through to the arch. Im not a welder all though studying engineering in school. Im not quite up to welding this. I was just wondering whether you need to leave wholes there?? Breathing?  :dontknow:

    

I think there must have been factory wholes there fr it to rust identically??

any help would be good as I need to get it welded up ASAP.

thanks

That area definitely needs welding/fixing! There are a couple of small slots where the outer sill joins to the inner, to serve as drain holes, there should be no others.

yes, definitely needs sorting. Ok, should I cut all of that area where it has broken away out and weld a plate in over it all??