Because of this new age that we're living in, everything is constantly changing, from the way we communicate, as well as education. English grammar is constantly changing---for example, the term "selfie" has been added to the Oxford English Dictionary. Almost on a daily basis, we encounter various idioms and other expressions, including ones we never knew existed.
Although these changes can be complicated for the most fluent of English speakers, it can be twice as complicated for those who consider English to be their second language. Many have felt discouraged because they may not know what sources to consider. Also, the current shortage of literacy tutors can slow the learning process.
Keeping up with reading can be a helpful tool, although it isn't easy for everyone. Another helpful tool is to consider a volunteer literacy program. Whether you decide to work one-on-one with a child or an adult student, becoming a volunteer tutor can be beneficial for both the student and the teacher. Not only can it boost the student's confidence, it'll also help you---the teacher---to learn more as you work together on a regular basis. Normally, volunteer tutors are expected to be available at least twice a week, so as not to overwhelm the student with a lot of work, especially if the student is struggling.
The are many sources for volunteer programs. Your local library also offers various information for literacy programs and courses.