***** NOT A TEACHER *****
Hello, Nuckri:
I think that the most important thing to remember about the passive is that one must use a form of the verb "be" and the past participle of the verb.
I have made up these examples. If you have any questions, please do ask (in a new thread), and many members will be delighted to help you.
1. I love broccoli. / Broccoli is loved by me.
2. Mona saw a movie. / A movie was seen by Mona.
3. They will visit a doctor. / A doctor will be visited by them.
4. Raul is typing an answer. / An answer is being typed by Raul.
5. We have already eaten breakfast. / Breakfast has already been eaten by us.
Well, I'm sure that you get the idea. As you know, in many cases it is not necessary to include "by ___." And, as you will have guessed, an active sentence needs an object (such as "broccoli" or "movie") in order to change it to the passive.
Have a nice day!