changes that cannot be made through the admin panel

Good afternoon.
I need to make some changes in the appearance of the theme VW Restaurant pro, how can I do these:
1) I need that by clicking on the links in the top menu, the page scrolls to the corresponding section on the page. For example, when you click on the “contacts” button, the page scrolls to the contacts block.
2) in the slider I need to change the color of the arrows leading to the next slide
3) in the slider I need the buttons to also scroll the site to the corresponding section, something like an anchor
4) in the header where the icons of social networks need to add an icon e- email and phone
5) when scrolling my top menu disappears, how can I make it not disappear.

The website address is gogicz.pl

I would be very grateful for your help.