I've {learned some | studied} English but I feel it’s still difficult to remember vocabulariesy and I couldan't speak well. I've {learned some | studied} English but I feel it’s still difficult to remember vocabulary and I can't speak well.

A vocabulary is a group of words; your vocabulary is all the words you know. “Vocabulary” is usually not countable.

I've learned (some) English but I feelit still feels difficult to remember vocabulariey words and I couldan't speak well. I've learned (some) English but it still feels difficult to remember vocabulary words and I can't speak well.

Changed couldn't to can't as you're talking about the present.

I will be happy to make friends here and. Please teach me English!! I will be happy to make friends here. Please teach me English!!

I will be'm happy to make friends here and tleach mern English!! I'm happy to make friends here and learn English!!

More natural to say learn instead of "teach me." I get that you probably were saying 教わる

Enjoy your time. Enjoy your time.

This sounds a bit odd. “Have a nice day” would sound more natural.

Enjoy your timI hope I enjoy my time here. I hope I enjoy my time here.

If you're using this as a goodbye, then just say "Have a good day" or "See you soon." If you're talking about yourself (enjoying Langcorrect), then follow the correction.

Wannko means puppy in Japanese, it'sand it's been my nickname for ages. Wannko means puppy in Japanese, and it's been my nickname for ages.

Wannko means puppy in Japanese, it'sand it's been my nickname for ages. Wannko means puppy in Japanese, and it's been my nickname for ages.

Put "and" because these could be two separate sentences (independent clauses). Need "been" after "it's".