I'm not a grammar god, and even less an expert on English style. I also speak and write the Northeastern US version of American English, which is not quite like the versions of English spoken and written in other parts of the US, let alone Canada, the UK, Ireland, and the other countries which were once part of the British Empire.

Your words are in italics; my suggestions are in bold type.

I would rewrite this to:

"I" is used as the subject of a sentence, not "me". A sentence needs a verb, which is why "I am", vs "Me". In English, periods are normally followed by one or two blank spaces, unless they end a paragraph.

Since I have registered, I have stayed here almost all day, because of the amazingly quick answers and many friendly monks.

I feel that my poor English is a barrier to communication.

The two grammar errors were the lack of a verb ("is") and the use of "barrier to communicate" (communicate is a verb) versus "barrier to communication" (communication is a noun). I also had four style issues: it's usually not considered good practice (in US English) to start a sentence with "and", "or", or "but," the word "indeed" was superfluous, and I don't like exclamation marks. The fourth style issue is that your sentence seems to be making a conclusion about what other Monks feel; this is why the "I feel" was added; it makes it clear that the sentence is a statement of your feelings.

I also feel that your English is not as much of a barrier to communication as you seem to think; it may be more of a problem for those Monks for whom English is not their first language, but the sense of your questions does come through.

I'm guessing, from your name that your first language is one of the languages Westerners lump into "Chinese." There are numerous sites on English grammar and usage, e.g., Guide to Grammar and Writing at the State of Connecticut's Capital Community College, or Lynch, Guide to Grammar and Style at Rutgers University.