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.
Best Answer
They were grammatical several hundred years ago, but are not used in contemporary English.
Today we would ask:
What did you do there?
using did as an auxiliary to form the past tense in combination with bare infinitive do.
What saw you there? would become today What did you see there?