"To be" sentence is : I have a car where "have" is used as main verb and there is no other verb in the sentence.
I'll have a last try too.
There's no way you could claim that "I have a car" is a "to be" sentence even if such a concept existed. "I am a car" might fit your definition.
"Been" is the past participle of 'to be'.
For example:
Walk: I walked; I have walked.
Sing: I sang; I have sung
Be: I was; I have been.
"I have been ..." is in the present perfect tense.
Now, there are two (at least) ways that this sentence can be finished: 1) with an adjective - "I have been
sick", and 2) as a passive construction - "I have been
abused". Either way, they use the present perfect tense of "to be". The second is in the passive voice of the present perfect tense.
If you still don't get it, why not put it aside for a few months and come back fresh to it?