I don't think hreflang tags are needed unless
You keep the main content in a single language and translate only the template, such as the navigation and footer. Pages that feature user-generated content, like forums, typically do this.
Your content has small regional variations with similar content in a single language. For example, you might have English-language content targeted to the US, GB, and Ireland.
Your site content is fully translated. For example, you have both German and English versions of each page.
If it is not your story then don't think about hreflang tags