Exactly, McTag. I would have said that if you hadn't.
In the States I'd recommend reading The New Yorker, a weekly magazine.
Thirst4- It helps if you can also be with people who have good grammar or at least LISTEN to people who have good grammar. Talking books are one way, public radio or classical music radio stations are another. Sad to say, at least in the States, many public educators cannot speak or write well. Do not always expect your teachers to be the best source.
I would recommend for study a terrific book that most American know:
The Elements of Style by Wm. Strunk (and later edited & revised by E.B. White). Rather than having incomprehensible rules, this book is a short series of essays on quality writing with many rewriting examples. Ahh, I found it online along with a huge source for more excellent writings -- Bartleby's!
Strunk's Elements of Style
Finally, check that you have learned your lessons by taking various online tests for grammar. See where your mistakes are made and study them.
Let's go over this study plan:
1. Read well-written works for enjoyment most of the time.
2. Listen to educated people who speak grammatically.
3. Study the Strunk book.
4. Test yourself to determine your weaknesses... concentrate on those.
5. Read more from Bartleby's.
6. Come back to a2k and we'll help.