You need to consider English, like any live language, as something you read, write, listen to and speak. To improve your skills you must try to do each of these daily. If you have no English speaker to talk to and you're a beginner, use DuoLingo online. It's free and does include some spoken opportunities. Once you can converse at least a little, practice going into a shop and asking for something.
Prepare for this by writing down what you want to say, speaking it aloud to yourself if you have no-one to listen, and then saying it for real in the shop. Try to remember what the shop person said in reply and practice that at home. For writing, read first. When you've read and understood a paragraph, write it out, then try to write the same meaning using different words.
