The Russian idiom, работать как лошадь, means to work hard, or literally ‘to work like a horse’. Another idiom with the same meaning is работать как проклятый (‘to work like the damned’) [source].
In English you might say that you’re working like a dog. Other variations on this phrase include wokring like a beaver and working like a trojan [source]. Do you know of any others?
In Welsh you might say that you’re working ‘to the marrow of your bones’ – gweithio hyd fêr dy esgyrn, which means to work for hard, or to overwork.
One equvialent in French is travailler comme un acharné (‘working like a relentless person’).
What about in other languages?
In Danish we might say “at knokle som en gal” – “to toil like a mad (one)”. The adjective “gal” means “mad”, “angry”, “crazy”, “insane”. A psychiatric hospital, for example, is called a “galeanstalt”, the second word in the compound, “anstalt”, being a slightly vulgar word for an institution of sorts, borrowed from German “Anstalt”.
In Swedish, we can say “arbeta som en myra / ett bi” (work like an ant / a bee),
sometimes even saying that a person is an “arbetsmyra” (worker ant)
when he or she is an avid worker.
You can also say that someone is “flitig som en myra” (working as if you are an ant)
(I do not know the English translation for “flitig”, but the end meaning is the same as above.)
In Brazilian Portuguese, “trabalhar feito um condenado”, literally “working like a convicted person”, or maybe “working like a prisoner”
A few friends and family members I know say that they “work like a madman”. Mainly hear it used to complain that they’re being overworked.