Hello Marinella,

Regarding FullCalendar, the first resource for you will always be FullCalendar's web page: https://fullcalendar.io/

To do what you wants, you need to configure the calendar (and use a little of JavaScript)

1. You need to provide the following JSON values in the Calendar's TextTimeCustomizationJSON property:

"views: {
        month: {columnFormat: 'ddd'}, 
        week: {columnFormat: 'ddd d MMM'}, 
        day: {columnFormat: 'ddd d MMM' }
},
dayNamesShort:['Dom','Seg','Ter','Qua','Qui','Sex','Sab']"

I have added the dayNamesShort to change the short names of the days (something it seems you already did).

2. Here, as far as I know, you need to do some JavaScript. First, I created a hidden input and button. the input will store the name of the view, while the button will execute an Ajax Submit to a Screen Action when the calendar executes the callback I add to the configuration:

"viewRender:function(view,element){
    $('#" + Input1.Id + "').val(view.name);
    $('#" + Button1.Id + "').click();
},

header: {
        left: 'prev,next today',
        center: 'title',
        right: 'month,agendaWeek,agendaDay'
},

theme: false,
firstDay: 0,
isRTL: false,
weekends: false,
fixedWeekCount: false,
weekNumbers:false,
height: 'auto',
contentHeight:'auto',
aspectRatio:'1.35',
eventLimit:'True'"

The second part after the viewRender property is just the default values of the Calendar's property you have to set this: GeneralDisplayJSON.

I attached an example you can use to study and adapt.

Cheers,
Eduardo Jauch