Getting type mismatch: inferred type is List but Collection was expected

Still stuck at this Breaking Bad API App. JSON model class is a list but when I'm calling the response in the global scope and putting it the mutable list it says type mismatch: inferred type is List but Collection was expected. How can i fix it

Main Activity

> class MainActivity : AppCompatActivity() {
> 
>     private lateinit var characterAdapter : MyAdapter
>     private var TAG = "MainActivity"
>     private var characterData= mutableListOf<ResponseBBItem>()
>     override fun onCreate(savedInstanceState: Bundle?) {
>         super.onCreate(savedInstanceState)
>         setContentView(R.layout.activity_main)
> 
>         characterAdapter = MyAdapter(characterData , this)
>         recyclerView.adapter = characterAdapter
>         val layoutMAnager = LinearLayoutManager(this)
>         recyclerView.layoutManager = layoutMAnager
>         getCharacterInfo()
> 
>         recyclerView.setOnClickListener {
>             getCharacterInfo()
>         }
>     }
> 
>     private fun getCharacterInfo() {
>         GlobalScope.launch(Dispatchers.IO) {
>             try {
>                 val response = Client.api.getInfo()
>                 if (response.isSuccessful) {
>                    val characterList = response.body()
>                     Log.d(TAG, characterData.toString())
>                     withContext(Dispatchers.Main) {
>                         if (characterList!= null) {
>                             Toast.makeText(this@MainActivity , "Data Loaded"

    enter code here

,Toast.LENGTH_SHORT).show()
>                             characterData.addAll(characterList.responseBB!!)
>                             characterAdapter.notifyDataSetChanged()
>                             tvText.text = characterList.toString()
>                         }
>                     }
>                 }
>             }
>             catch (e:Exception){
>                 withContext(Dispatchers.Main){
>                     Toast.makeText(applicationContext, "Cannot Load Data" , Toast.LENGTH_LONG).show()
>                 }
>             }
>         }
>     } }

I'm getting the error at characterData.addAll(characterList.responseBB!!)

APIRequest

interface APIRequest {

    @GET("character/random")

    suspend fun getInfo() : Response<ResponseBB>
}

ResponseBB

data class ResponseBB(

    @field:SerializedName("ResponseBB")
    val responseBB: List<ResponseBBItem?>? = null
)

I believe that 2 ?s in List<ResponseBBItem?>?are giving me error

ResponseBBItem

data class ResponseBBItem(

    @field:SerializedName("birthday")
    val birthday: Any? = null,

    @field:SerializedName("img")
    val img: String? = null,

    @field:SerializedName("better_call_saul_appearance")
    val betterCallSaulAppearance: Any? = null,

    @field:SerializedName("occupation")
    val occupation: List<String?>? = null,

    @field:SerializedName("appearance")
    val appearance: List<Int?>? = null,

    @field:SerializedName("portrayed")
    val portrayed: String? = null,

    @field:SerializedName("name")
    val name: String? = null,

    @field:SerializedName("nickname")
    val nickname: String? = null,

    @field:SerializedName("char_id")
    val charId: Int? = null,

    @field:SerializedName("category")
    val category: String? = null,

    @field:SerializedName("status")
    val status: String? = null
)

Client

object Client {

    val gson = GsonBuilder().create()
    val retrofit = Retrofit.Builder()
        .baseUrl("https://www.breakingbadapi.com/api/")
        .addConverterFactory(GsonConverterFactory.create(gson))
        .build()

    val  api = retrofit.create(APIRequest::class.java)
}

MyAdapter

class MyAdapter(var listChar : List<ResponseBBItem?>, val context : Context) : RecyclerView.Adapter<MyAdapter.MyViewHolder>() {
    class MyViewHolder(itemView : View): RecyclerView.ViewHolder(itemView) {
        var name = itemView.findViewById<TextView>(R.id.tvName)
        var occupation = itemView.findViewById<TextView>(R.id.tvOccupation)
        var protrayed = itemView.findViewById<TextView>(R.id.tvActor)
        var status = itemView.findViewById<TextView>(R.id.tvStatus)
        var appearance = itemView.findViewById<TextView>(R.id.tvAppearance)
        var image = itemView.findViewById<ImageView>(R.id.ivImage)
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        val view = LayoutInflater.from(parent.context).inflate(R.layout.item, parent , false)
        return MyViewHolder(view)
    }

    override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
       holder.appearance.text = listChar[position]!!.appearance.toString()
        holder.name.text = listChar[position]!!.name
        holder.occupation.text = listChar[position]!!.occupation.toString()
        holder.protrayed.text = listChar[position]!!.portrayed
        holder.status.text = listChar[position]!!.status
        Picasso.get().load(listChar[position]!!.img).into(holder.image)
    }

    override fun getItemCount() = listChar.size

}