Hey! Firstly I’d say take a look at deploy contexts and you might like to redirect by conditions (language and country), you can view those here: File-based configuration | Netlify Docs
Also, there is a nice guide on redirects here: [Support Guide] Making redirects work for you - troubleshooting and debugging that could come in handy!
In the instance above for your redirect I think you could do something like
/de-ch/* /de-ch/404 404
I think this should redirect any route that does not already exist to your 404 with a 404 error code.
I would still recommend looking at the links above and I personally find the syntax of netlify.toml redirect with conditions much nicer to understand.
IE:
Language redirect without netlify toml:
/* /de-ch/:splat 302 Language=de-ch
with netlify.toml
[[redirects]]
from = “/”
to = “/es”
status = 302
force = true
conditions = {Country = [“ES”]}