You could create a injectContentManagerComponent and add this to app.js - from that point (react component) you are free to go as you like.
The simplest but maybe not cleanest solution would be to monitor the url and enforce the same language via url.
However: There might be a better solution by using things that useCMEditViewDataManager or something like that might be offer you for your demand. 
Another option could be to use the famous/infamous patch-package and create a patched version of your current strapi-version and overwriting the redirect after saving an entity there.