Per my research, there is no dedicated endpoint in Microsoft Graph to get SharePoint Group permissions and their members currently.
You only could get the id of Microsoft 365 groups in which the current user is a member.
Here are steps:
1.Get the user id by using following graph query.
https://graph.microsoft.com/v1.0/users?$filter=displayName eq 'DisplayName'
2.Get the Microsoft 365 group display name and id by using following graph query.
https://graph.microsoft.com/v1.0/users/{userid}/memberOf/microsoft.graph.group?$select=displayName,id
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