Working Template Excel project navigation with Gantt Diagramm

Hello, all Excel members, I'm currently trying to make a working Excel table that could have an assigned task, members, start and stop date (stop should be calculated from start date + working days).
I have a template that I'm working on, but if someone has a working one it would be appreciated.

The problem that I had was not to count weekends, I just hid the Saturdays and Sunday.
But the formula for counting the days and the corresponding diagram is not correctly represented.
One day is missing from a chart, and at some cells, I see it is well drawn.

The second thing I want to have is that once Excel sees a team member's name he sees the previous task, and calculates the start of the next task once the previous one is completed (column end date ).
Because I don't add sequentially all the tasks to one person and then assign tasks for the next one memeber.

The third task is to have the possibility to add a color to each member in a task Gantt diagram.

Let me know your suggestions, I downloaded a template from Office 365 but it is not perfect and there I started.