Improving my game code

One variable per line please.

int gess,i=0,found=0,  r = rand()%100;

This makes the code hard to read. There is also one corner case (with pointers) were this will not work as expected for beginners. As a result this is usually banned in most companies coding standards.

You are using found as a boolean variable.
Treat it as such. use TRUE/FALSE.

I would change the while() into a for(;;) loop. Then you can remove all the increments.

while (i<10 && found==0)

--

for(int i = 0; i < 10 && !found; ++i)

White space is your friend:

if (found==1&&gess==1)  // This is hard to read and will get worse with more conditions.

if (found && (guess == 1)) // much more readable
//  ^^^^^  boolean use it as such.

Your "st", "nd", "rd", "th" is not correct.

10-19    => th
x1       => st
x2       => nd
x3       => rd
x[4-9]   => th

Also you print basically the same string every time on success. So we not have one print statement and just separate the logic for getting the ending. I would change the logic:

if (!found)
{
    printf("\n Never mind try again");
}
else
{
    char const* ext = "th";
    if ((gess < 10) || (gess >= 20))  // 10->19 already set
    {
        int end = gess % 10;
        if      (end == 1) { ext = "st";}
        else if (end == 2) { ext = "nd";}
        else if (end == 3) { ext = "rd";} 
    }

    printf("\n Very good the number is %d this is your %d%s gess", gess, i, ext);
}

#include<stdio.h>
#include<stdlib.h>
#include <time.h>



int main()  // Main always return int ...ALWAYS...
    {
        printf("\t\tWelcome to our gessing game\n\n\n");   // This could be device specific. If i run it on a minimized screen it might look akward

        /*
            maybe, call a function like take_device_width() then use the value returned to
            print the welcome message
        */
        printf("the computer choose a random number between 1-99, try to gess the random number...");

        /* You could write something like this

            #define MIN_NUM 1
            #define MAX_NUM 99

            printf(""The Computer chooses a random number between %d and %d. \
                   You have to guess it using minumun number of guesses\n", MIN_NUM, MAX_NUM);

            So that when ever you want to change the values for number range you can just
            change it once at pre processor macro.

        */

        srand(time(NULL));     // srand((unsigned) time(NULL));

        /* Dont use bad spellings and always indent code cleanly: i,e int guess, i = 0, found = 0*/

        int gess,i=0,found=0,  r = rand()%100;

        /* INstead of saying that number of guesses is i, you can name it as num_of_guesses. So that next time
           when you look at code you will know what num_of_guesses does . Similarly for r.
        */

         /* Instead of using magic number 10, you could write it as a macro:

            #define MAX_ATTEMPTS 10

        */


        while (i<10 && found==0)        // indent it here: while(num_of_guesses < MAX_ATTEMPT && found == 0)  
        {
            printf("\n My gess is:\t"); // no need of \t here
            scanf("%d",&gess);

            /* Indent it. After a block that does something add a comment of what next block does nad write that code */
            if (gess==r)
            {
                found=1;    // instead of found we can do this

                /* if(guess == r)
                   {
                        num_of_guesses++;
                       printf("You guessed the correct answer in %d guesses", num_of_guesses);
                       exit(0);
                   }

                   will avoid checking for while(condition) even after guessing correct answer
                */
                i++;
            }

            else if(gess>r)
            {
                printf("\n Too big\n");
                i++;
            }
            else                            // else is enough here
            {
                printf("\n Too small\n");
                i++;
            }

            /* most of the newline char are unneccesary */
        }

        /* Indent here */

        /* This looks daunting. What are you trying to do here. Why so many conditions */

        if (found==1&&gess==1)
            printf("\n Very good the number is %d this is your %dst gess",gess,i);
        else if(found==1&&gess==2)
            printf("\n very good the number is %d this is your %dnd gess",gess,i);
        else if(found==1&&gess==3)
            printf("\n very good the number is %d this is your %drd gess",gess,i);
        else if(found==1&&gess!=1&&gess!=2&&gess!=3)
            printf("\n very good the number is %d this is your %dth gess",gess,i);
        else
            printf("\n Never mind try again");
        getchar();

        /* it could be 
         * if(num_of_guesses >= MAX_ATTEMPTS)
           {
               printf("You couldn't guess it in suggested attempts. Sorry!");
               exit(1);

               you can even add a yes or no condition to play again

           }

        */
       return 0;
    }// end main