How to clone a project to existing directory containing files

I have an account on https://gitlab.com. I’ve created a project and it is available on https://gitlab.com/my-username/my-project

I already have files on my local computer under /var/dev/project. I would like to “sync” my project on GitLab with a local directory.

When I issue the clone command inside the local project directory I get a new directory inside my local project.

/var/dev/project$ git clone git@gitlab.com:my-username/my-project.git

/var/dev/project$ ls
my-project

When I issue the clone command outside the local project directory I get an error.

/var/dev$ sudo git clone git@gitlab.com:my-username/my-project.git

git@gitlab.com: Permission denied (publickey,keyboard-interactive).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

I would like to “sync” existing /var/dev/project directory and its content with the gitlab.com project. How to do that?