My program jump over to case condition although the condition don't was true

Question

I have problem with switch statement. Like you see I have condition like expression and I have 3 cases (0, 1, 2). To get an overview, this function is three-way handshake between client and server. In case 0 the program going to receive SYN and try to send ACK + SYN in case 1. But when checksum is incorrect the program jump over to case 1 and send ACK + SYN. You can see the print "Im here" with condition value do not show "Im here 4" also the program know we have wrong checksum but still it goes over to case 1. Help me :(

    int Server_ThreeWay_Handshake(int fileDescriptor, fd_set *activFdSet, struct sockaddr_in *client)
{

    short int condition = 0;                // Using in switch for different condition
    short int run = 0;                      // Using in while loop
    short int Window_Size = rand() % 7 + 1; // Generat window size
    short int i = 0;                        // Using for while loop

    fd_set readFdSet;
    RTP Read;
    RTP Write;
    struct timeval timer;

    int len = sizeof(struct sockaddr); // Used in recvfrom to send len of sockaddr

    do
    {
        switch (condition)
        {

        case 0:{ // In this case the SYN goint to be recevied
            printf("Im here 1: %d\n", condition);
            readFdSet = *activFdSet;

            if (select(FD_SETSIZE, &readFdSet, NULL, NULL, NULL) < 0)
            {
                perror("\x1b[31mServer: select fail!\x1b[0m\n");
            }

            if (FD_ISSET(fileDescriptor, &readFdSet))
            {
                printf("Im here 2: %d\n", condition);
                // If we recevied some SYN
                if (recvfrom(fileDescriptor, &Read, MAXMSG, 0, (struct sockaddr *)client, &len))
                {
                    printf("Im here 3: %d\n", condition);
                    int Read_CheckSum = Read.CheckSum;
                    CheckSum_Function(&Read);

                    if (Read.SYN == true && Read.CheckSum == 10)
                    {
                        printf("Server: revevied SYN with SEQ number: \x1b[32m%d \x1b[0m With CheckSum: \x1b[32m%d\x1b[0m\n", (int)Read.SEQ), Read.CheckSum;
                        printf("Im here 4: %d\n", condition);
                        // Controll window_size and set it to Length if Length is < window_size
                        if (Read.Length < Window_Size)
                        {
                            Window_Size = Read.Length;
                        }
                        condition = 1;
                    }
                    else
                    {
                        printf("Im here 5: %d\n", condition);
                        printf("\x1b[31mServer: Incorrect checksum\x1b[0m\n");
                    }
                    
                }
                
            }
            
        }
        case 1:{ // In this case server send ACK on SYN to client
            printf("Im here 6: %d\n", condition);
            Set_Default_Values(&Write); // Set to default
            Write.ACK = true;
            Write.SYN = true;
            Write.Length = Window_Size;
            strcpy(Write.Data, "SYNACK"); // Save SYN like text in Data for checksum
            SEQ_Generator(&Write);        // Generate SEQ to ACK
            Write.ACK_Number = Read.SEQ;

            do
            {
                // Sending ACK + SYN
                CheckSum_Function(&Write);
                sendto(fileDescriptor, &Write, sizeof(Write), 0, (struct sockaddr *)client, sizeof(*client));
                printf("Server: send ACK + SYN number: \x1b[32m%d\x1b[0m, with SEQ number: \x1b[32m%d\x1b[0m with checksum: \x1b[32m%d\x1b[0m\n", (int)Write.ACK_Number, (int)Write.SEQ, (int)Write.CheckSum);

                timer.tv_sec = 1;
                timer.tv_usec = 0;
                readFdSet = *activFdSet;

                // Using select for timeout
                if (select(FD_SETSIZE, &readFdSet, NULL, NULL, &timer) == -1)
                {
                    printf("\x1b[31mServer: select failed!\x1b[0m\n");
                }

                if (FD_ISSET(fileDescriptor, &readFdSet))
                {

                    // Recevied last ACK from client
                    short int Recevied_Last_ACK = recvfrom(fileDescriptor, &Read, MAXMSG, 0, (struct sockaddr *)client, &len);
                    int checkSum = Read.CheckSum;
                    CheckSum_Function(&Read);

                    if (Recevied_Last_ACK == 0)
                    {
                        Set_Default_Values(&Read);
                    }
                    if (Read.ACK == true && Read.ACK_Number == Write.SEQ && checkSum == Read.CheckSum)
                    {
                        printf("Server: recevied ACK number: \x1b[32m%d\x1b[0m with checksum: \x1b[32m%d\x1b[0m\n", (int)Read.SEQ, (int)Read.CheckSum);
                        condition = 2;
                    }
                    else
                    {
                        printf("\x1b[31mServer: Don't recevied ACK from client or the checksum is incorrect!\x1b[0m\n");
                        i++;
                    }
                }
                else
                {
                    printf("--- Timeout ---\n");
                }
                if (i > 0)
                {
                    exit(EXIT_FAILURE);
                }

            } while (condition == 1 && i <= 3);
        }
        case 2:{
            LastReceviedSEQ = Read.SEQ;
            printf("\n--- Server: Three-way handshake successful --- \n");
            printf("\n--- The window size is %d ---\n", Window_Size);
            break;
        }
        }
    } while (run == 1);
}