SQL Server, behöver guidning!

using(SqlConnection dbConn = new SqlConnection(connString))
            {
                SqlCommand cmd = new SqlCommand(sp, dbConn);
                cmd.CommandType = CommandType.StoredProcedure;
               
                addVehicle.VehicleType = UserInputHandler.GetVehicleType();

                if (addVehicle.VehicleType == "Car")
                {
                   
                    addVehicle.VehicleRegNumber = UserInputHandler.GetVehicleRegNumberHandler();

                    cmd.Parameters.AddWithValue("@VehicleType", addVehicle.VehicleType);
                    cmd.Parameters.AddWithValue("@VehicleRegNumber", addVehicle.VehicleRegNumber);
                    cmd.Parameters.AddWithValue("@VehicleArrivalTime", DateTime.Now);

                    SqlParameter vehicleID = new SqlParameter("@VehicleID", SqlDbType.Int);
                    vehicleID.Direction = ParameterDirection.Output;
                    cmd.Parameters.Add(vehicleID);
                               
                    cmd.Parameters.AddWithValue("@PSpaceNumber", 1);
                    cmd.Parameters.AddWithValue("@PSpaceSize", 2);
                    cmd.Parameters.AddWithValue("@PSpacesRemaining", 1);

                    SqlParameter parkingSpaceID = new SqlParameter("@ParkingSpaceID", SqlDbType.Int);
                    parkingSpaceID.Direction = ParameterDirection.Output;
                    cmd.Parameters.Add(parkingSpaceID);
                   
                    try
                    {
                        dbConn.Open();
                        cmd.ExecuteNonQuery();
                        TextToUser.PrintVehicleAdded();
                    }
                    catch (Exception msg)
                    {
                        TextToUser.PrintExceptionMessage(msg);
                    }
                   finally
                    {
                        dbConn.Close();
                    }
                }

CREATE PROCEDURE spAddVehicle
@VehicleType NVARCHAR(10),
@VehicleRegNumber NVARCHAR(10),
@VehicleArrivalTime DATE,
@VehicleID INT OUT,
@PSpaceNumber INT,
@PSpaceSize INT,
@PSpacesRemaining INT,
@ParkingSpaceID INT OUT
AS
BEGIN
INSERT INTO Vehicles(VehicleType, VehicleRegNumber, VehicleArrivalTime) VALUES (@VehicleType, @VehicleRegNumber, GETDATE())
SELECT @VehicleID = SCOPE_IDENTITY()
BEGIN
INSERT INTO ParkingSpace(PSpaceNumber, PSpaceSize, PSpacesRemaining) VALUES (@PSpaceNumber, @PSpaceSize, @PSpacesRemaining)
SELECT @ParkingSpaceID = SCOPE_IDENTITY()
END
END

IF(PSpaceNumber "Någon operator" "Variabel")
BEGIN
INSERT INTO ParkingSpace?
END

CREATE PROCEDURE spAddVehicle
@VehicleType NVARCHAR(10),
@VehicleRegNumber NVARCHAR(10),
@VehicleArrivalTime DATE,
@VehicleID INT OUT,
@PSpaceNumber INT, //Denna?
@PSpaceSize INT,
@PSpacesRemaining INT,
@ParkingSpaceID INT OUT
AS
BEGIN
INSERT INTO Vehicles(VehicleType, VehicleRegNumber, VehicleArrivalTime) VALUES (@VehicleType, @VehicleRegNumber, GETDATE()) 
SELECT @VehicleID = SCOPE_IDENTITY()
BEGIN
DECLARE @NextSpace INT
SET @NextSpace  = (SELECT COUNT (*) FROM ParkingSpace) +1 //Ligger den rätt här? 
BEGIN
INSERT INTO ParkingSpace(PSpaceNumber, PSpaceSize, PSpacesRemaining) VALUES (@PSpaceNumber, @PSpaceSize, @PSpacesRemaining) //Bör jag ändra något från parametrarna här?
SELECT @ParkingSpaceID = SCOPE_IDENTITY()
END
END
END

[ParkingSpaceID]   INT IDENTITY (1, 1) NOT NULL,
    [PSpaceNumber]     INT NOT NULL,
    [PSpaceSize]       INT NOT NULL,
    [PSpacesRemaining] INT NOT NULL,
    PRIMARY KEY CLUSTERED ([ParkingSpaceID] ASC)

[VehicleID]          INT           IDENTITY (1, 1) NOT NULL,
    [VehicleType]        NVARCHAR (10) NOT NULL,
    [VehicleRegNumber]   NVARCHAR (10) NOT NULL,
    [VehicleArrivalTime] DATETIME      NOT NULL,
    [ParkingSpaceID]     INT           NOT NULL,
    PRIMARY KEY CLUSTERED ([VehicleID] ASC),
    CONSTRAINT [FK_ParkingSpaceID] FOREIGN KEY ([ParkingSpaceID]) REFERENCES [dbo].[ParkingSpace] ([ParkingSpaceID])

CREATE PROCEDURE spAddVehicle
@VehicleType NVARCHAR(10),
@VehicleRegNumber NVARCHAR(10),
@VehicleArrivalTime DATE,

@PSpaceSize INT,
@PSpacesRemaining INT
AS
BEGIN
INSERT INTO Vehicles(VehicleType , VehicleRegNumber, VehicleArrivalTime) VALUES (@VehicleType, @VehicleRegNumber, GETDATE())
BEGIN
DECLARE @PSpaceNumber INT
SET @PSpaceNumber = (SELECT COUNT(*) FROM ParkingSpace) + 1 
BEGIN
INSERT INTO ParkingSpace(PSpaceNumber, PSpaceSize, PSpacesRemaining) VALUES (@PSpaceNumber, @PSpaceSize, @PSpacesRemaining)
RETURN @PSpaceNumber
END
END
END

using(SqlConnection dbConn = new SqlConnection(connString))
            {
                SqlCommand cmd = new SqlCommand(sp, dbConn);
                cmd.CommandType = CommandType.StoredProcedure;
               
                addVehicle.VehicleType = UserInputHandler.GetVehicleType();
                
                if (addVehicle.VehicleType == "Car")
                {
                    addVehicle.VehicleRegNumber = UserInputHandler.GetVehicleRegNumberHandler();
                    addVehicle.VehicleRegNumber = addVehicle.VehicleRegNumber.ToUpper();
                    cmd.Parameters.AddWithValue("@VehicleType", addVehicle.VehicleType);
                    cmd.Parameters.AddWithValue("@VehicleRegNumber", addVehicle.VehicleRegNumber);
                    cmd.Parameters.AddWithValue("@VehicleArrivalTime", DateTime.Now);

                    //SqlParameter vehicleID = new SqlParameter("@VehicleID", SqlDbType.Int);
                    //vehicleID.Direction = ParameterDirection.Output;
                    //cmd.Parameters.Add(vehicleID);
                    //SqlParameter parkingSpaceID = new SqlParameter("@ParkingSpaceID", SqlDbType.Int);
                    //parkingSpaceID.Direction = ParameterDirection.Output;
                    //cmd.Parameters.Add(parkingSpaceID);

                    SqlParameter pspacenumber = cmd.Parameters.Add("@PSpaceNumber", SqlDbType.Int);
                    pspacenumber.Direction = ParameterDirection.ReturnValue;
                    cmd.Parameters.AddWithValue("@PSpaceSize", 2);
                    cmd.Parameters.AddWithValue("@PSpacesRemaining", 0);

                    try
                    {
                        dbConn.Open();
                        cmd.ExecuteNonQuery();
                        TextToUser.PrintVehicleAdded();
                    }
                    catch (Exception msg)
                    {
                        TextToUser.PrintExceptionMessage(msg);
                    }
                    finally
                    {
                        dbConn.Close();
                    }
                }