28. We usually chat with our friends in English so that we can improve our English communication skills. (TO)
→ We usually chat with our friends in English to improve our English communication skills.

29. My brother notes down new words to learn them later in his free time. (AS)
→ My brother notes down new words as a way to learn them later in his free time.

30. It is important that we review the lessons several times before the test. (LOOK)
→ It is important to look over the lessons several times before the test.

31. Surfing websites can help us learn English because they provide a wide range of vocabulary and grammar. (BECAUSE OF)
→ Surfing websites can help us learn English because of the wide range of vocabulary and grammar they provide.