How to fix append error in MySQL in ASP.NET MVC 5?

Question

ASP.NET

Good afternoon!
I am working on a project in ASP.NET MVC 5.
There are two models LanguageList and LanguageInfo. The LanguageList stores all the possible languages ​​that the user can select, and the LanguageInfo stores the ones that the user has chosen. Actually here is the code:

LanguageList.cs

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web;

namespace CRM.Models
{
    public class LanguageList
    {
        [Key]
        public int Id { get; set; }
        public string Name { get; set; }

        public ICollection<LanguageInfo> LanguageInfos { get; set; }

        public LanguageList()
        {
            LanguageInfos = new List<LanguageInfo>();
        }
    }
}

LanuageInfo.cs

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web;

namespace CRM.Models
{
    public class LanguageInfo
    {
        [Key]
        public int Id { get; set; }
        [Required, Display(Name = "Уровень владения языком")]
        public int SkillLevel { get; set; }
        [Required, Display(Name = "Родной язык")]
        public bool NativeLanguage { get; set; }

        public int LanguageListId { get; set; }
        public LanguageList LanguageList { get; set; }

        public ICollection<BridgeLC> Categories { get; set; }
        public ICollection<BridgeTL> Translators { get; set; }

        public LanguageInfo()
        {
            Categories = new List<BridgeLC>();
            Translators = new List<BridgeTL>();
        }

        public void AddCategory(CategoryInfo categoryInfo)
        {
            Categories.Add(new BridgeLC()
            {
                CategoryInfo = categoryInfo
            });
        }

        public void AddCategory(int categoryInfoId)
        {
            Categories.Add(new BridgeLC()
            {
                CategoryInfoId = categoryInfoId
            });
        }
    }
}

There is also a model for displaying the user's profile - TranslatorAdd.cs, which stores the data that he has chosen, the code:

TranslatorAdd.cs

namespace CRM.ViewModels
{
    public class TranslatorAdd
    {
        public Translator Translator { get; set; } = new Translator();
        public LanguageInfo LanguageInfo { get; set; } = new LanguageInfo();
        public CategoryInfo CategoryInfo { get; set; } = new CategoryInfo();
        public LanguagePair LanguagePair { get; set; } = new LanguagePair();

        public int TranslatorId
        {
            get { return Translator.Id; }
            set { Translator.Id = value; }
        }

        public int LanguageInfoId
        {
            get { return LanguageInfo.Id; }
            set { LanguageInfo.Id = value; }
        }

        public int CategoryInfoId
        {
            get { return CategoryInfo.Id; }
            set { CategoryInfo.Id = value; }
        }

        public int LanguagePairId
        {
            get { return LanguagePair.Id; }
            set { LanguagePair.Id = value; }
        }


        //[Display(Name = "Выберите язык")]
        //public int LanguageId { get; set; }
        //[Display(Name = "Уровень владения языком")]
        //public int CategoryId { get; set; }

        public SelectList LanguageSelectList { get; set; }
        public SelectList CategorySelectList { get; set; }
        public SelectList SpecialitySelectList { get; set; }
        public List<SelectListItem> JobTypeSelectList { get; set; }
        public List<SelectListItem> ExpertLevelList { get; set; }

        SelectList Result { get; set; }

        

        public void Init(LanguageListRepository languageListRepository,
            CategoryListRepository categoryListRepository, SpecialityListRepository specialityListRepository)
        {
            int selectedIndex = 1;
         
            LanguageSelectList = new SelectList(
                languageListRepository.GetList(),
                "Id", "Name");

            CategorySelectList = new SelectList(
                categoryListRepository.GetList(),
                "Id", "Name", selectedIndex);

            SpecialitySelectList = new SelectList(
                specialityListRepository.GetListByCategoryId(selectedIndex),
                "Id", "Name");

            ExpertLevelList = new List<SelectListItem>()
            {
                new SelectListItem() { Text="Интересуюсь", Value="low"},
                new SelectListItem() { Text="Часто использую в повседневной жизни", Value="medium"},
                new SelectListItem() { Text="Есть опыт работы в данной области", Value="high"},
                new SelectListItem() { Text="Есть проф. образование", Value="pro"},
            };

            JobTypeSelectList = new List<SelectListItem>()
            {
                new SelectListItem() { Text = "Письменный перевод", Value = "written translation"},
                new SelectListItem() { Text = "Устный, последовательный перевод", Value = "Consecutive interpretation"},
                new SelectListItem() { Text = "Устный, синхронный перевод", Value = "Simultaneous interpretation"},
                new SelectListItem() { Text = "Редактура", Value = "editing"},
                new SelectListItem() { Text = "Копирайтинг", Value = "Copywriting"},
                new SelectListItem() { Text = "Контроль качества", Value = "Quality control"},
                new SelectListItem() { Text = "Корректура", Value = "correction"},
            };
        }  
    }
}

And the View itself:

TranslatorAdd.cshtml

<div class="tab-content">
            <div class="tab-pane active" id="language_1">
                <div class="mt-lg-5">
                    <div class="form-group row">
                        <div class="col-sm-6">
                            @Html.LabelFor(m => m.LanguageInfo.LanguageListId, new { @class = "col-form-label float-sm-right" })
                        </div>
                        <div class="col-sm-6">
                            @Html.DropDownListFor(m => m.LanguageInfoId, Model.LanguageSelectList, new { @class = "form-control" })
                        </div>
                    </div>

                    <div class="form-group row">
                        <div class="col-sm-6">
                            @Html.LabelFor(m => m.LanguageInfo.SkillLevel, new { @class = "col-form-label float-sm-right" })
                        </div>
                        <div class="col-sm-4">
                            @Html.EditorFor(m => m.LanguageInfo.SkillLevel, new
                       {
                           @class = "slider col-form-label float-sm-left",
                           @type = "number",
                           @min = 0,
                           @max = 100,
                           @step = 1
                       })
                        </div>
                    </div>
}

I do according to the CodeFirst principle. Tables for models are created, but when I try to send data, I get this error:

Picture with error