I don't know how it works for Pakistani nationals generally, or Pakistani nationals based in UAE specifically. Nor do I know how it works for people of your trade.

However, it is probably advisable for you to wait until the visa has been issued before you hand in your resignation from your current position.

There have been some problems in the past, generally speaking, about delays in issuing visas.

I cannot say whether or not this might apply in your case, but it is better to be safe than sorry. In the past, some people have been offered a job and then resigned from their jobs and worked their notice, but there has been a delay in processing their visas, and so they have ended up 'between jobs' and unemployed for a few months.

Make sure that doesn't happen to you. Wait until the visa is actually issued.

I do not know if there are any issues relating to exit visas. Other people may answer your question.