Callithump, hello again.

Since I posted corrections on another thread, I'll take this one on too.

"since a long time ago" is not correct. "since" is a preposition and needs a noun or pronoun as its object, which "a long time ago" strictly isn't. Better would be, "for a long time".
"composing" generally refers to writing music; "writing" would be better in this context. "it" at the end of the sentence -- what does this refer to? (every pronoun must refer to a noun); "it" would be better left out. The sentence would therefore be better, "I feel awkward in writing, so I'm trying to write diaries in English to practice, but I don't feel confident ("unconfident" is not a word).

You're doing great!