The word "But" connects this verse to the previous verse about the hypocrisy of the Pharisees. (See: [[rc://en/ta/man/translate/writing-connectingwords]])
"everything that is hidden will be shown." This can be stated in active form. AT: "people will find out about everything that people do secretly" (See: [[rc://en/ta/man/translate/figs-activepassive]])
This means the same thing as the first part of the sentence in order to emphasize its truth. It can also be stated in active form. AT: "people will learn about everything that others try to hide" (See: [[rc://en/ta/man/translate/figs-parallelism]] and [[rc://en/ta/man/translate/figs-activepassive]])
Here "darkness" is a metonym for "night" which is a metonym for "private. And "light" is a metonym for "day" which is a metonym for "public. The phrase "will be heard" can be stated in active form. AT: "whatever you have said privately at night, people will hear it in the daylight" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-activepassive]])
Houses in Israel had flat roofs, so people could go up and stand on top of them. If readers would be distracted trying to imagine how people would get up on the house tops, this could also be translated with a more general expression, such as "from a high place so that everyone will be able to hear."