1, One of your classmate is not good at speaking what can you advise her to do for improving?

Make friends

Make friends with English speakers or others learning to speak English and compare notes. Talk about things that you have learnt and exchange ideas.

Do interesting activities in English

Take a cooking course in English or join a book club! Anything you enjoy doing, make sure you do it and communicate it in English. Using English to talk about things you enjoy will make practising a positive experience.

Have a debate

Debate all the topics that interest you with friends in English. Try to use as much vocabulary as you can to get your point across and listen to the other arguments carefully so you can argue against them effectively.

Use a dictionary

Online dictionaries often have audio examples so you can check your pronunciation and there are lots of great dictionary apps that you can take everywhere with you on your smartphone. Make sure not to become too reliant on these tools, though. Have a go at saying the words first then check afterwards to see if you were right!
2. what do you think with what kind of methods one can improve their critical thinking?
Critical thinking is a valuable skill to have in your toolbox. Honing this skill set may help you tackle everyday decisions and excell in new areas of your professional life.
In a study conducted by Global Strategy Group found that today's young professionals are lacking in the skills most prioritized by business leaders and it's not the skills you may be thinking - like technical or specialized skills - as critical thinking skills topped the list. What does this mean? If you want to stand out at work or in a job interview, you may need to improve your critical thinking skills.

1. Know exactly what you want

Knowing exactly what you want is the first step of critical thinking.
We have to think critically to solve problems so that they meets their objectives. Every decision we make has an objective or purpose attached to it and identifying exactly what that is, what we actually want out of it, gives us a starting point to work with.
So ask yourself: What do I want? What do I expect to get out of this? Until you know the answer to these questions you're not going to know what the right decision is.