I have been away for many days away from this great webpagsite, for several reasons. I have been away for many days from this great website, for several reasons.

The main one iwas that I was too busy in my studies. The main one was that I was too busy in my studies.

Later I get theot COVID, and in those dayduring which I felt very sick. Later I got COVID, during which I felt very sick.

"in those days" would be used when talking about the distant past or historical events.

The lLast Tuesday, a guy from the university has saitold me that I could applying for a scholarship to study abroad. Last Tuesday, a guy from the university told me that I could apply for a scholarship to study abroad.

He said that likely I could be benefited with itit could likely be awarded to me, so I'm very excited. He said that it could likely be awarded to me, so I'm very excited.

When talking about receiving scholarships in English, we almost always use "awarded" or "granted".

I need to write a motivation letter, but I'm worry about my grammar in this languageEnglish. I need to write a motivation letter, but I worry about my grammar in English.

You haven't mentioned which language previously in the text, so I would be specific here. I'm assuming you mean English in the correction.

Now, I'm looking for people who canould correct my letter in order toso that it "sounds" more natural. Now, I'm looking for people who could correct my letter so that it "sounds" more natural.

"can" implies people who have the ability. "could" more implies people the have the ability and are willing to correct your letter.