Fixed header and adding number in header

Hi All experts,

I need your input in the issue I have been trying to fix from the last 1 week.
The site is https://www.cithubdev.com.au/myhelpsite/

2 issues are
1. I have managed to add phone number is header some how using css.
the code I used in CSS manager
p.telnumber {color:#ccc;font-size:20px;float:right;}
p.telicon {color:#6B6C6D;font-size:20px;float:right;}

and in header.php I have added
<p class=”telnumber”><b><b>0449 191 689 </b></b></p>
<p class=”telicon”><i class=”fa fa-phone”></i></p></br />

but the problem is how can i change the font size and family. I tried doing that in css but it is disturbing phone icon as well.

2. I have made the header fixed for mobile devices but when i selct any menu item it is scrolling and hiding the title. the code i used for this is below
@media (max-width: 768px){
#main-nav, #main-nav.fixed {
position: fixed;
}}

FYI – I am making all these changes in CSS manager plugin

Please advise solution or some way around for these 2 problems.