Self-study means learning something by yourself. (Interrogative)

It helps you so that you can understand things at your own speed. (Simple) = It helps you to understand things at your own speed.

So, no other way of learning is so good as self-study. (Affirmative) = Self-study is the best way of learning.

By reading books, you can learn many things. (Complex) = If you read books, you can learn many things.

Self-study makes you more confident because you solve problems of your own. (Simple) = Self-study makes you confident because of solving problems of your own.

When you read alone, you can choose the area of your study. (Compound) = You read alone, and you can choose the area of your study.

Regular self-study can make you successful in school and in life. (Complex) = If you practise self-study regularly, you can be successful in school and in life.