Hi @Naama Almog ,
To List a user's memberships (direct and transitive):
var graphClient = new GraphServiceClient(requestAdapter);
var result = await graphClient.Users["{user-id}"].TransitiveMemberOf.GetAsync();
For different SDK's there are snippets here please check them: https://learn.microsoft.com/en-us/graph/api/user-list-memberof?view=graph-rest-1.0&tabs=http#request
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