I think the most burdensomehardest thing about Japanese is the honorifics. I think the hardest thing about Japanese is the honorifics.

Today, I sendt e-mails to my university registrar to ask a question. Today, I sent e-mails to my university registrar to ask a question.

Today, I send e-mails toemailed my university registrar to ask a question. Today, I emailed my university registrar to ask a question.

Today, I sendt some e-mails to my university registrar to asking a question. Today, I sent some e-mails to my university registrar asking a question.

The question iwas quite simple, but writing the e-mails bothered me. The question was quite simple, but writing the e-mails bothered me.

The question is quite simple, but writing e-mails bothereds me. The question is quite simple, but writing emails bothers me.

"Writing emails bothers me" = in general, I don't like to write emails. "Writing the email bothered me" = there was something about this particular email I didn't like.

The question iwas quite simple but writing the e-mails bothered me. The question was quite simple but writing the e-mails bothered me.

It is not easy for me to use honorifics correctly. It is not easy for me to use honorifics correctly.

You can also say "It's" instead of "It is".

I don't usually use such rigidthe most formal honorifics, and there are many manners ondifferent rules of etiquette for business. I don't usually use the most formal honorifics, and there are many different rules of etiquette for business.

I don't usually use such rigid honorifics, and there are many manners on businessto follow. I don't usually use such rigid honorifics, and there are many manners to follow.

What you wrote is not wrong, but the meaning sounds strange. When you say "business," do you mean the social interaction with the registrar? Typically, "business" is used to discuss economy or companies in English, or maybe specific tasks.

I don't usually use such rigid honorifics, and there are many manners odifferent ways to do it in business. I don't usually use such rigid honorifics, and there are different ways to do it in business.

What is the most complicated inaspect of English? What is the most complicated aspect of English?

What is the most complicated inaspect of English? What is the most complicated aspect of English?

Or "part of the English language."

What is the most complicated inpart of English? What is the most complicated part of English?