Floorpan + Frame Rail/Structural Rust Repair advice.

[BadDays]

Folks, I need guidance on how to fix this monstrosity, My e30 has some of the worst rust in the passenger floor and the frame rail is exposed, Checking the car from underneath shows that the entire floor pan is compromised and will need replacing, The transmission tunnel is alright but this is what it looks like:
I'm able to weld and cut metal but I need advice for how to proceed with this repair, Any Help Is appreciated.

[Vincenze]

Replacement floor pans are available.

Check videos from this body guy.

https://www.youtube.com/watch?v=d2r1LfxY61M

[BadDays]

Replacement floor pans are available.

Check videos from this body guy.

https://www.youtube.com/watch?v=d2r1LfxY61M

To update you and everyone else, The frame rails are good for now but I'll be cutting and welding in a new lower firewall section for the floors and frame rails since the rust has eaten some of the metal from the otherside of that photo. The driver's side is thankfully less work and won't need extensive repairs but needless to say I'll be ripping out the carpet in the late summer/fall and fixing this disaster before it gets any worse 🙂↕️

Thanks for the link!