A French Bulldog will do best when walked at least once everyday for 20 minutes per day.
If not possible to walk the French Bulldog everyday then you need to walk the French Bulldog around at least every 2 to 3 days to keep them healthy and well exercised.
If you don't walk the French Bulldog at least every two days then the French Bulldog could become overweight and become unhealthy as a result.
So it's best to walk the French Bulldog at least everyday to keep the dog healthy as well as keeping yourself healthy so it's a win, win situation as you both get the needed exercise to stay healthy.