Certainly vizualisation shouldn't be the only method you use to practise and learn a foreign language but it can be a very effective way, especially when you're somewhere native speakers of the language are rare.
I'm currently enjoying an older out of print book called "Breakthrough Greek" to develop my understanding of modern Greek a bit further. The beauty of their approach is using short dialogues with explanations on the facing page. I first read the dialogue through without reference to the vocabulary or explanations and see what my brain can work out based on what it already knows or can guess. Then I read the vocab and explanations and reread the dialogue and practise saying it out load. I've already learnt the alphabet but if I was learning that too I would write the passage out. I then visualize having the conversation with another person. I mentally substitute some of the words with others I know. If the dialog covers stuff that's very new to me I leave it for a day or so then come back to it - this gives my brain time to have rewired. When I do meet a helpful native speaker I try some of it out.