The word "testimony" can be expressed with the verb "testify." Also who they testified about can be stated clearly. AT: "by what they said when they testified to others about Jesus" (See: [[rc://en/ta/man/translate/figs-abstractnouns]] and [[rc://en/ta/man/translate/figs-explicit]]) (See: [[rc://en/ta/man/translate/figs-synecdoche]]).
The believers told the truth about Jesus, even though they knew that their enemies might try to kill them because of it. AT: "but they kept testifying even though they knew that they might die for it"
The devil is spoken of as if he were a container, and anger is spoken of as if it were a liquid that could be in him. AT: "He is terribly angry" (See: [[rc://en/ta/man/translate/figs-metaphor]])