English tenses. What used correctly?
"They danced all night" or "They were dancing all night" or "They had been dancing all night"
"She told the truth" or "She was telling the truth" or "She had been telling the truth"
"He walked some time" or "He was walking some time" or "He had been walking some time"
"He sat for an hour" or "He was sitting for an hour" or "He had been sitting for an hour"
"He warned her" or "He was warning her" or "He had been warning her"

Question

Answer

The key to using these past narrative forms is that they don't work in isolation.  You use them all in relation to each other.  As James has suggested, you need to look up these grammar forms (past simple, past continuous, past perfect and past perfect continuous) and study how they work together.

Answer

They are all correct in the appropriate contexts. It depends on what you are trying to say. You'll want to read up on continuous and perfective verb aspects in a text book or other resource.

Answer

All good but..

"He walked FOR some time" or "He was walking FOR some time" or "He had been walking FOR some time"