How can I improve my eyesight I have been wearing glasses sonce im 7 I am now 20?

See ophthalmologist. Other than contacts or glasses, the other options are what is called refractive surgery of which the most used is lasik surgery. You are near the end of changes which usually stop in the mid 20's. Discuss this with your ophthalmologist.
You can't. . Your level of refractive error is genetically determined for the most part. Glasses & contact lenses are the main sources to help you see clearly. Surgery, such as lasik, is considered for those where glasses/ contact lenses are not a suitable option.