The Perfect Progressive Theory in Bulgarian grammar refers to the verb tense that describes an ongoing action or state that has been completed in the past. It is formed by combining the Perfect and Progressive aspects of the verb.

To form the Perfect Progressive tense, we use the auxiliary verb “съм” (to be) in the Present Perfect tense, followed by the auxiliary verb “бил” (have been) in the past participle form, and then the main verb in its present participle form.

For example, to say “I have been working”, we would say “Аз съм работил” or “Аз съм бил работил”.

This tense is often used to emphasize the duration of an action or state that started in the past and continued until a specific point or still continues in the present. It can also be used to express an action that is expected or planned to occur in the future.

It is important to note that the Perfect Progressive tense is not as commonly used in Bulgarian as in English, and its usage may vary depending on the context and the speaker.