Regarding expenses in gst

How to add GST Expenses in GST Portal ? Is it necessary to add expenses monthly or we can adjust expenses at the year end ?

Person managing business from home so how much expenses allowed to purchase stationary and other miscellaneous item for home expenses ?

Nature of business is proprietor then how many employee/staff he can hire ? What is cash limit for salary ?

Is there any expenses list available i.e head wise ?

Regards