Fix the problem on the site on the front side (laravel)

Good afternoon.

Website on laravel

Video problems https://disk.yandex.ru/i/EoIA0Izd4vCktQ

Conclusion from our backend programmer

The problem is that the front does not remember the chosen time. That is, after an error, the selected time flies away but is displayed as selected. Because of this, after an error as in the video, the user will have to choose the time one more time. If we take the case as in the video. You have to choose another time and then press again at 10:30. Or click again at 10:30 a.m.


How much will this work cost and the deadline for its implementation?