updated work on existing project md

docs/user_guide/work_on_existing_project.md

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+# Collaborating on an Existing DevOps / DSO / DVC Project
+
+If a DSO project is already set up and you want to collaborate or extend it, follow these guidelines. For general information about DSO or DVC, please check out the [DSO getting-started page](../getting_started.md) or the [DVC documentation](https://dvc.org/doc).
+
+## Requirements
+
+- The original project was initialized with `dso init` and contains all essential files.
+- A DVC remote storage is set up where all DVC-controlled data is stored.
+- A Git repository exists and can be cloned.
+
+## How-To
+
+### Clone the Git Repository
+
+First, clone the existing git repository of the project.
+
+```bash
+git clone <git_repository>
+```
+
+### Pull the Data from the Remote Repository
+
+After cloning, no DVC-controlled input or output data is locally available. Therefore, it is required to pull the data associated with the repository from the DVC remote storage. Use:
+
+```bash
+# Compiles all params.in.yaml into params.yaml files and pulls the DVC-controlled data
+dso pull
+```
+
+### Make changes to DSO Project
+
+After pulling the source code from the git repository and the respective data from the DVC remote storage, everything is set-up to make changes and expand on the dso project. Please follow the instructions on how-to set-up folders, stages, or configuration files described in the [dso getting-started page](../getting_started.md).