Thanks for coming back to me and offering to help.
Here's a page preview link. The text is in Greek so it will look a bit confusing. The menu header's width looks normal on a laptop screen, but not on a regular screen and the padding/ margin at the bottom is completely off across all devices.
I am aware that it is limited but my company wants to use the available Hubspot tools and then in a year's time when the website grows a bit more & our strategy evolves, they'll reconsider migrating the website to a new theme. Your theme looks fantastic by the way!
Simple way to add a sticky menu to Hubspot's Sprout theme
I only recommend tinkering with the code if you're proficient in HTML/CSS. Otherwise I recommend either engaging a HubSpot CMS developer or leveraging the Marketplace for a Module which can add this functionality for you out of the box.
Dave Roma, HubSpot CMS Developer
Build a revenue generating website on HubSpot without a developer using The Generator Theme