I have been interested in learning English 语法有错吗顺便问一下understand的过去分词

I have been selling I have been trying I have ever been I too have been I have been to. I have been I have been in. I have been reading your newspaper for many year with a great enthusiasm and interest.这里enthusiasm不是不可数吗,怎么用a呢 I have been there,have been 是have been in还是have been to的缩写? i have always been there i have never been there I HAVE NEVER BEEN,能否说I never have been I have been so serious I have been so serious I-have-been-at-home I have always been you I have been loving you I have been a person . I have never been away! I have been wet through