webpage shows different homepage on mobile than on desktop

i have a problem with my website when its moving on towards the mobile mode, the web page its showing a different homepage on the mobile than on the desktop
i have setup the homepage to static and the post to the correct post page but instead its showing a post on mobile as the home page
Any ideas why is the reason this is happening?
i am using a built in word press theme and have tried looking into the settings but i haven’t had any luck