You have loved for six years
No, that sentence is not correct. That sentence should be: If you have been in love for 6 years.
No, the correct phrasing would be "It has been 5 years since I have known him."
No - the sentence 'Had never been experience' is not a correct sentence.
It has been 5 years since you knew him.Read more: It_has_been_5_years_since_you_knew_him._Is_this_sentence_grammatically_correct
Dr. Andre has been your dentist for years. Is he very very gentle?
"He could not have been there" is the correct sentence. It conveys the idea that he was unable to have been at the specified place.
The family dog might have been decrepit,but he was well-loved.
Being able is the correct version of the sentence. You can use it as a fragment of any sentence.
The correct sentence is: "Have you ever traveled before?"
A central fund for EGMM has been opened.
Yes, "How long have you been living in Oxford?" is a good sentence.
The use of the word in the sentence you quote is in the sense of having been perceived as being rude to an elder. So yes, the sentence is correct.