To find the Fortbyte number 59 of the decryption challenge, grab the Durrr! emoji (step 53 of the battle pass, paid version), then go to Mega Mall, in the Pizza Pit restaurant more precisely. The restaurant is located east of Mega Mall and you will recognize it thanks to the holographic tomato floating above.
Go to the kitchens behind the counter to find the Fortbyte, don't forget to activate the Durrr! emoji so that it can be picked up.
Written by Augustin "TheGreatReview" Héliot. Translated from French by Millenium.us.org