Hi joy 🙂 thank you for contacting us

please share your website URL and login information to check it out better ( check the set as a private reply )

However, you can enable the my account following path :
WordPress dashboard -> theme setting -> topbar -> Login/My-account Button

https://imgur.com/tm32jEf

Regarding the size of my account icon in the mobile header, I can give you code to decrease the size of the button.