Here's what happens:
* Snape's initial response: After Harry reveals Voldemort is invading his dreams, Snape scoffs and dismisses it, telling Harry to "stop being so melodramatic."
* Snape's later help: When Harry continues to suffer from nightmares, he seeks Snape's help again. This time, Snape takes the issue more seriously and suggests using a "dreamless sleep potion." However, Snape is hesitant to help, stating that the potion is "not entirely legal."
It's important to note that Snape is trying to help Harry, but his methods are limited by his own personal beliefs and fears. He doesn't want to risk using magic that is not approved by the Ministry, even if it means helping Harry.
The issue of Voldemort's intrusion into Harry's dreams is later addressed in the books, but not through private instruction from Snape.