Hello sir I want to improve my erection?

See a urologist. What exactly is the problem? You are very young to be having erectile problems. Go see a urologist to have a full evaluation.
Find the cause first. To assess if one's erections have weakened, he should visit a primary doctor, who can check for possible causes: stress, depression, diabetes, high blood pressure, low testosterone, artery disease, high cholesterol, smoking, older age, etc... Causes found can be treated to help make erections stronger, firmer, longer lasting. A urologist can evaluate. Meds like viagra, cialis, or Levitra (vardenafil) may help.