How do I turn a real-life problem into an algorithm?

Start at the end. What is the final result you want? Then work backward. If you want to build an app that finds the cheapest suya in town, what's the first thing you need to know?

You need a list of suya spots. Then you need their prices. Then you compare them. Breaking it down this way is called Decomposition. It's the first step to being a great coder.