@hajrovica. Well, now I am trying to put the current date and an id to the invoice but I still do not know how it can be done, do you have any idea?

Ok ... Lets clarify some things

You want to put current date to invoice? Or a date when invoice is created? In my logic useful thing would be date when invoice is created ...

In case of current date you could go for something like:

 {{Carbon\Carbon::now()->toDateTimeString()}}

that will just output current date/time in view, and i am not saying this is good practice though again in my view it is better to print out date related to invoice... For getting date using Eloquent, check https://laravel.com/docs/5.3/eloquent-mutators

About id? what kind of id is it? Number of invoice or something else, i cant say because i do not have larger "view" of app and what is exact approach for managing invoices. If i recall your want to pass $cart variable, retrieved from session, to view? Is that order somehow stored/saved, what if user wants to print some old order and so on ...