Reading other people's sentences, whether in the textbook, in a book, on your phone or online IS EASY! Writing our own sentences is much harder. So, don't just read the examples in the book and keep going.
Once you have read and understood the grammar, the key is to look for examples of the grammar in other writing and make a collection of these sentences from natural texts. The best way is to open an article from a newspaper online and CTRL + F and search for the key word relating to that grammar. For example "have" and "has" if you are looking for present perfect.
Once you have found them save the sentences in a word file and look at the different ways that they are formed, let the similarities and differences between them become clear over many examples.
After that, think about your own life, and when you might need to use this grammatical form. Then write down your sentences.
Bring them to you teacher or to your friends, or just try them out and see what response you get. Either way - it has taken a lot more effort than just reading and continuing.