In literature I meet such questions: What did you there? What do you then? Why are they grammatically correct?
Pussycat pussycat, where have you been? I've been up to London to visit the Queen. Pussycat pussycat, what did you there? I frightened a little mouse under her chair
In another source of this poem I saw 'what you did there?'
"We will need men," Zouga said. "What will you do when you have them?" Jan Cheroot asked. "Dig the stuff out." "And then?" the little Hottentot demanded with a malicious gleam in his dark eyes, his features wrinkled as a sour windfallen apple. "What do you then?" he insisted.