Formal:
* Huwag kang magmadali. (Literally: Don't hurry.)
* Dahan-dahan lang. (Literally: Slowly only.)
Informal:
* Wag kang mag-alala. (Literally: Don't worry.)
* Enjoy lang. (Literally: Just enjoy.)
* Walang problema. (Literally: No problem.)
More specific:
* Kumuha ka ng oras. (Literally: Take your time.)
The best choice will depend on the situation and your relationship with the person you're talking to.