I inspected your website. The actual size of the menu items is 30px not 150px because 150px is too large font size for text. I was able to increase or decrease the font size in Google’s code inspector tool.
Do you remember what was the font size of the menu items before changing the theme and is it just the font size that changed or anything else too after changing the theme? Also, can you please share the login credentials of your website because I am not seeing any issue while inspecting the code?