public class Project
{
    public Guid Id { get; set; }
    public guid ProjectTypeId{ get; set; }
    public string projectType{ get; set; }
    [Required]
    public DateTime CreationDate{ get; set; }
    //more properties here
    //...
    public bool Activated{ get; set; }
    public IList<ProjectDetail> ProjectDetails{ get; set; }
}

public class ProjectDetail
{
    [Required]
    public Guid Id { get; set; }
    public Project Project{ get; set; }
    [Required]
    public Guid ProjectId{ get; set; }
    public string DetailDescription{ get; set; }
    public IList<ProjectDetailsAnswer> ProjectDetailsAnswers{ get; set; }
}

public class ProjectDetailsAnswer
{
    [Required]
    public Guid Id { get; set; }
    [Required]
    public Guid ProjectDetailId{ get; set; }
    public ProjectDetail ProjectDetail{ get; set; }
    public string OtherField{ get; set; }
    [Required]
    [MaxLength(512)]
    public string AnswerDescription{ get; set; }
}

public class ProjectViewModel
{
public Guid Id { get; set; }
public List<KeyValuePair<string, List<string>>> Details { get; set; }
}

var data = _dbContext.Project
.Select(p => new ProjectViewModel
{
    Id = p.Id,
    Details = p.ProjectDetails
        .Select(pd => new KeyValuePair<string, List<string>>(pd.DetailDescription, pd.ProjectDetailsAnswers.Select(pda => pda.AnswerDescription).ToList())
        .ToList()
})