I thought you ... (to look through) the contract at 5

I thought you were looking through the contract at 5 oclock yesterday.  

Я мыслил, что вы просматриваете договор в 5 часов вчера.

The first part of the sentence is in Past Indefinite and the second part is in Past Continuous.

The keywords are at 5 oclock yesterday. Past Continuous is formed with the help of the second form of the auxiliary verb to be was / were and the suffix ing. (Was is used with singular and were is used with plural).

Negative was / were + not + verb + ing. (You were not looking).

Interrogative was / were + subject + verb + ing. (Were you looking?).