If you are a new learner take your time to think about your answers but if you are a more advanced learner  you can give yourself an extra challenge by setting a  time limit. Start by allowing yourself 2 minutes to answer these 15 questions (that’s 8 seconds per question which is the usual amount of time you should allow yourself in language tests such as the TOEIC® and TOEFL®) and then try again getting faster and faster. 

https://english-podcasts.com/english-grammar-speed-test/