Not exactly. Spermatogenesis, the process by which sperms are produced, takes around 2-3 months to finish. Taking this into account, an improvement in your sperm count will not happen earlier even if you follow a special diet, take supplements, avoid harmful habits, etc. It does not take place from one day to the next.
It should be clear that improvements depend on the origin of your problem. If the reason why your sperm count is low is caused by agents that are not related to your lifestyle, your sperm count is not going to improve.