Each of the following sentence is not correct in standard English

IV. Each of the following sentence is not correct in standard English.
Identify and correct the mistakes
1. Preserving natural resources mean reserving them for our future.
2. Regardless of your teaching method, the objective of any conversation class
should be for students to practice speaking words.
3. In order for one to achieve the desired results in this experiment, it is
necessary that he work as fastly as possible.
4. Happiness is a most important thing in my life. Nothing is more valuable.
5. The most wood we use, the more trees are being cut down.