Challenge JavaScript Bug fix

Hello Friends, I have a new offer for you. If you are interested, please feel free to provide an information about the estimated delivery time and a price. I want to fix some bugs and add a new features to the open source application, which can be found at: https://github.com/sboard-team/whitebophir-old. I'm JS Developer and I'm so busy now so I have to give a part of this work to the others. The work is very easy if you really understand the code and have done a similar job. I mean experience. I've fixed over 40 bugs in this app and I've changed database from MongoDB to JSON file. I love JSON ❤️ The power of simplicity. IMPORTANT: I don't have time to negotiate a price so tell me your fixed price.
Details in the attachment.