"There is very little milk left."
Translation:Der er meget lidt mælk tilbage.
That is indeed how it is said in Danish. Many Danes make the mistake of saying "There's no milk back" etc. when learning English.
In terms of understanding the spatial conception of tilbage, it can be helpful to translate 'tilbage' as 'remaining'. Then, you will easily see the connection: 'There is very little milk remaining'. And we do this in English to, compare 'we stayed back' with 'we remained'.
This of course won't help for temporal usage, where 'back' is again the better translation. 'TIlbage i marts' = 'back in march'.