Studying English with a friend who is not a native English speaker is both good and bad. You should be aware of the pros and cons of speaking with a non native speaking friend. Practicing with a non native person will give you practice. You can also motivate each other and point out basic mistakes. But you might pick up bad habits from one another if you are not sure about what are correct and incorrect sentences. So use these practice times as a time period to practice the correct material you studied. Not to learn how to say a sentence.