I got my first client, but I'm confused about something, could you help me figure it out?

So basically, I'm pretty new to developing websites, but I still managed to learn the basics using YouTube videos. I installed the free version of the Elementor plugin, but I'm not able to edit my header and footer with it. Could you suggest an easy plugin that includes most features? Also, I'm confused about how to make the 'View All Services' and 'Know More About Us' buttons clickable and how to add services inside them, as shown in this picture. Please help