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Lifestyle changes is the first step in improving the quality and quantity of spem.
Stress relief, avoiding smoking
and alcohol, avoiding tight fitting underwear, weight reduction if obese would all would improve sperm count
Treat the infection you have.
If all these measures fail, then surgical conditions like varicocele
should be ruled out with a doppler scan of the scrotum
If there is no varicocele, then you can try taking supplements like L carnitine to improve the count and motility of sperm.
Hope that answers your question.