Topic sentence
It's better to study offline.
A. Support Points: Advantages of offline
       1. Offline helps me to focus more
       2. easier to listen to the teacher
       3. Having friends should be more fun
B. Supporting point: disadvantage of online
       1. network or malfunction, some of you do not have the means to access the internet
       2. Don't focus on the lesson
       3. It is easy for bad guys to enter the classroom
Concluding sentence
    Offline learning is much more convenient.

in my opinion,  studying offline is the best choice for me:

-first of all, i can focus more on my lecture 

easy to study by ourself without lack of concentration

i can talk to my friend about my opinion of the lesson and ask them if necessary

-secondly, i can do exercise and ask the teacher without waiting for minutes because of lacking internet 

teacher can check my exercise and correct them if there are  some mistakes 

-finally, i don't have to focus on the screen to much while studying online, i can see lively my lesson at school.

to sum up, studying offline is my best choice.