Home office deductions & mortgage interest on Sch A

I have my business home office expenses to deduct for 2020 taxes. I have listed mortgage interest & property taxes in Sch A. Does this mean, I can’t enter those to as home office? (10% business use)

 

if so, wouldn’t it make more tax advantage to enter all mortgage related items on business then Sch A?

 

also, mortgage payments are not deductible? Only interest is? I can’t use full payment I pay each month? (Interest + principle)