Yes, it's perfectly okay to say that, I checked. Here's other phrases you might wanna use:

"Ramadan kareem" (which means "have a generous Ramadan") or

"Ramadan mubarak" (which means "have a blessed Ramadan").

The sun's longer and it won't be easy this year or so I've learned. I don't know what else to say, I don't have a Muslim friend or co-workers, never had any. If anyone wants to share something, I'd be happy to educate myself more on the subject.