I have repeatedly searched for this on Google or other sources, but haven't found anything suitable for my problem, try to help me to resolve this
'Normal' java objects inside of your Model String, int, Date, etc are already handled by gson, but to deserialize custom objects inside of a model you'll need to register your own custom serialization. Check out this: https://futurestud.io/tutorials/gson-advanced-custom-deserialization-basics