Slider, page font and menu font problems

Hi All,
After installing Theme Forest Jevelin I run into several problems that I can not fix.
First, the homepage is very slow in loading, the nice slider revolution does not fit the whole screen but stays below the headers, I can not style the menu buttons in a good reading font and or color and on my mobile I get a jquery problem.
Would anybody please have a look? My website is: https://birdwatchingalentejo.com
Thanks in advance

Hello :smiley:

You are welcome to contact the author of that theme if you like. Here is their support information - https://themeforest.net/item/jevelin-multipurpose-premium-responsive-wordpress-theme/14728833/support

Thanks!