There are many, many courses of English taught in English. Quite a lot of these are available as video lessons for free on YouTube. Some of the free online courses are produced by professional educators, while others are taught by amateurs.
When you choose a textbook to help you with your English, keep one thing in mind: Can I use this textbook without a teacher to guide me?
A good course will have comprehensive explanations and answers for the independent reader.
Printed Textbooks[]
One of the most widely used courses for English as a Second Language is the four-book series Side By Side by Steven Molinsky and Bill Bliss.
Side By Side is a text-heavy book. Many of the grammatical examples are repeated several times in the lesson and the exercises.