Question

Помогите в Passive voise. Please, help me. 11. The briefing is in full swing. The correspondents are interviewing the participants of the conference. 12. The company was developing a new project. 13. You can't watch the film now. The mechanic is fixing the TV set

Answer 1

11. The briefing is in full swing. The participants of the conference  are being interviewied  by the correspondents .
12. A new project was being developed by the company
13. You can't watch the film now. The TV set is being fixed by the mechanic 

Answer 2

Of course, I'd be happy to help you with passive voice for the given sentences. To change these sentences to passive voice, we need to restructure them so that the subject becomes the receiver of the action rather than the doer of the action.

11. The participants of the conference are being interviewed by the correspondents. (Passive voice)

12. A new project was being developed by the company. (Passive voice)

13. The TV set is being fixed by the mechanic. (Passive voice)

Keep in mind that in passive voice, the structure is generally: [Receiver of the action] + "be" verb (am, is, are, was, were, etc.) + past participle of the main verb (usually ends with -ed, -en, or -d). In some cases, the tense might change depending on the original sentence.