How does a restaurant make money after paying for rent for the building, paying employees, food, drinks, etc?

It's a tough business even during good times and many restaurants go out of business.  How do they make $?  By having a large volume of customers, eliminating poor selling items on the menu and by the sale of alcohol.    Some restaurants depend on beer and wine sales to make a profit.

That one,s poorly chasing anything,if that,s wrong,God there too,doesn,t step in,pelting in it.

The things you mention are their overhead, so at the end of the month they either gained in net or took a loss which means in order for them to make money, what they made in money for the month has to be above their over head, their bills which are their expenses. This is why some businesses close or file bankruptcy,  if their sales are not above their expenses they are taking a loss...

 If they made more money in sales than their expenses, then they are making money

Big mark up on food

Because they charge £8 for a couple of prawns as a starter, £30 for a steak my butcher would charge £5 ( supermarket £3.50), £5 for a slice of gateaux or cheesecake that costs £8 for a 30 portion size and £30 for a bottle of £6 wine.

However, as you say, they have large overheads and if there aren’t enough customers, losses can be massive.

Watch Gordon Ramsey’s kitchen nightmares.

From the profits made from the food / meals they sell?

They don't make money, they make food.

They charge enough for what they serve to make a profit after the expenses.

A restaurant actually makes most of it's 'profits' selling the drinks rather than the food.

Think about it ..

A bottle of wine that you can by in a shop for €5 they will sell for anything up to €25

.. and, because they buy in bulk (straight from the supplier) they get it much cheaper as well.

By charging enough on the menu to cover the expenses and have a bit of profit.