Welcome @Chandima1
We have a guide here with many details. → What should I do if my data exceeds the given 250GB of storage?
For the exact details, you will need to review the terms of service at the server where you are working. All will have slightly different data retention times.
In general, it is a good idea to save back a copy of anything important to a storage location where you have full control (backups secured). See → FAQ: How can I reduce quota usage while still retaining prior work (data, tools, methods)?
If you have followup questions about a specific server, you can share back the URL and we can try to clarify about it more (will need to be public).
Hope this helps! 