Adding things in header

I made my first wordpress website a few weeks ago. I did this with the Divi theme I bought via Elegant Themes. I am using WordPress 4.1.2 with the Divi Child Theme. The website name is http://www.alonamedia.com (it´s a Dutch site). I would like to know if it would be possible to add extra´s on my website. For example I want to add a phone number in fat letters in the header on right side. Is this possible, and if so, can I do it myself or can you do this for me? If you need to do this for me, how much would it cost to do this?

My second question is if it is possible to make the slider on the home page thinner? If so, how do I do this?

Thank you in advance and I hope you can help me!