Searching for values in a small list without using nested IFs

Hello everyone!

I created this scheduler that shows appointments when you provide the days and a starting date. Problem is when I input a date that doesn't match the days selected I want the sheet to look for the next available day and start from there. For example: I select Fridays and Saturdays as the days but I introduce a date that happens to be a Monday, what I'm looking for is for it to look for the next Friday and start counting from there.

I found a very long solution with several nested IFs, since I want to improve my skills I was wondering if there is a cleaner way to do it.
What do you suggest? I'm attaching a sample so you can see for yourselves what I'm talking about.

Data and formulae scatter all over the spreadsheet; hard to understand what u need, say where is the input condition and where is the output

But by intuition, Match or Frequency function could possibly come into play.