The joining date is not determined after signing the offer letter. What to do?

Dear sir/madam,

I am on a visit visa currently. I have signed an offer letter (no MOHRE contract yet). They didn't inform me of the joining date yet.

Also, I'm wondering what are the next steps. They informed me in the offer letter that an employment visa will be provided from the company's end. But they didn't even ask for any documents yet (such as a passport copy, visit visa copy, etc).

If this is something unusual as per UAE's law. How can I deal with it?