Hi @Pramitha,
A warm welcome to the Bunnings Workshop community and thank you for your question.
Repairing the render itself is fairly simple and you can use How to repair a rendered wall from @Nailbag as a guide, but if the underlying issue is not fixed, then it will reappear over time.
If this wall is retaining soil from the townhouse complex or is structurally supporting the townhouses in any way, then this could indicate a potentially major issue that should not be covered up or taken lightly.
The cracking render indicates there is movement beneath and it looks like the crack is following the mortar lines of a besser block wall. In the best-case scenario, the movement is because of settlement, but if the movement is because the wall is not adequate to retain or support what it is supposed to, then it could be a major issue waiting to happen.
I would suggest contacting an engineer for their assessment and the Body Corporate Manager for the townhouse complex to discuss your concerns. An engineer will be able to offer recommendations, and the Body Corporate manager will be able to coordinate repair efforts with the neighbours.
Let me know what you think and if you have further questions, please don't hesitate to ask.
Jacob
