There are several good reasons for learning English.
1. In countries where English is not the primary language, being able to communicate in English translates to a better paying job.
2. Understanding English widens the social and professional groups of people that you can meet.
3. After mastering the English language you can begin teaching it.
4. Learning any language is great exercise for the brain.
Those are a few ideas. I hope that helps. Use an English language spelling and grammar checker, like that found in Microsoft Word, before you submit your homework to your teachers.