You cannot restore the db to the default mendix db but you can install postgres and restore to a db on it.
See https://docs.mendix.com/developerportal/howto/restore-backup-locally for more details
Hope this helps
For the code you need access to the teamserver of that project. The person who created the project can give access. In the modeler you can then select Open App and you will see all the Apps you have access to. You can then select the main line to download the complete Mendix model.
For the data see Dragos answer. You are able to also upload a complete backup. See the docs here: https://docs.mendix.com/howto/tips/migrating-your-mendix-database