Hi @Rene115 ,
This is a hot topic.
To get the weekend days, you can check this post,
Next, I suppose you will need to check for availability.
I am doing a replacement for date picker with custom list and soon will be integrated into my free template, Komun.
The benefit of doing in list is we have more control on how to show and to add actions with conditional, but we need to build calendar database which are inconvenient to most people, it adds more complexity than normal which they are trying to avoid by using no code tools.
But if you are the type of person that move forward with whatever the roadblocks are, I think booking function is achievable.