Remove value from Drop-Down menu if selected before

Hi @Yusuf_128,

Welcome to the community.
I wrote a blog post about 4 years ago for an appointment system tackling this issue.
If someone chooses an appointment from a dropdown, it is removed for the following user. I am sure you can apply the same concept for your solution.
 

• Appointment System Solution for SharePoint On-Premise

Hi Simon ,

Thanks for the information but i dont have any database i can use. Is there any diffrent way i can accomplish this?

You can enforce unique values in the list column settings. You can find those under the list settings of sharepoint. It won’t prevent users from selecting the option but it will prevent them from saving the new item.

SharePoint and Nintex have databases, so your environment has an SQL server.
If IT will not create a new database for you to use, see if they can add a table to one of the existing databases.  It's not ideal, but it would work.

The other option may be to use a SharePoint list. To select a date, use a date control. Make sure the control is configured not to allow past dates.
Then, cascade the available times off of the date selected. I haven’t tried it, but it should work.
If no times are available for the selected date, then no times will appear in the cascaded lookup.