As for the prices in restaurants, the average check for dinner for two can cost you from €40.If you plan to cook yourself, shopping here is very simple. It is better to buy fruits and vegetables from local farmers, their vans you can meet almost on every corner, and meat - in butcher shops. Everything else you can buy in local stores or supermarkets (the biggest ones are Lidl and Pavi Pama). To understand the price level: for €2 you can buy a kilogram of oranges, for €10 - a rabbit carcass.
Malta has a lot of amazing places to see, so in my opinion, the minimum number of days for this island is at least ten. To be honest, in a year and a half of living in Malta I haven't fully explored it, and I am still discovering new places that fascinate me with their beauty!