Vocabulary comes with practice. Some people can learn a word a day, or ten words a day etc but the system doesn't work for everyone. Don't just do exercises from textbooks. Read in English as often as you can. Read newspapers, magazines, websites - as long as they're written in decent, formal English, you will pick up a lot of vocabulary. Don't look up every single word you read. You've already found that that takes too long. Frequently, you can guess at the meaning of a word from the context and the words around it. Listen to English radio but don't concentrate on it. Just play it in the background as often as you can. Watch films and TV shows in English if you can. Watch videos on ted.com. Again, don't stress about every single word. The more you read/listen/watch, the more you will pick up.
As far as your written English is concerned, remember the following:
- Start every sentence with a capital letter.
- Always capitalise the word "I".
- End every sentence with a single appropriate punctuation mark(full stop, question mark, exclamation mark).
- Do not put a space before a comma, full stop, question mark or exclamation mark.
- Put a space after a comma, full stop, question mark or exclamation mark.
- The ellipsis (...) has a particular use. Don't use put several full stops together for no reason.