What does this rebus means ?

PROG WORKRESS

Outside a tattoo artist's shop, there was a signboard which read 'I make tattoos on only them who do not tattoo themselves'.

Reading it what do you think, does the tattoo artist tattoo himself?

What work can one never finish?

You are mixing a mixture of cement and Sand with five gallons of water. You have a garden hose giving you all the water you need. The problem is that you only have a four-gallon bucket and a seven-gallon bucket and neither has graduation marks. Find a method to measure five gallons.

What has to be broken before you can use it?

Place a mathematical symbol between the numerals 5 and 9 in such a way that the resulting number is greater than 5 but smaller than 9.

A pond had 60 fish, out of which, all but 20 died.
How many fishes are now present in that pond?

13 decks of cards have been mixed. What is the minimum number of cards that must be taken out from the above-mixed cards to guarantee at least one 'four of a kind?

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?

Use only one mathematical symbol and all numbers (0-9) to get a sum of 99