I am stuck with the Q $9.$ Please help me with it$,$ thanks!

$[1]$ Suppose that $15$ years ago you bought a home for $$500,000,$ paying $20\%$ as a down payment, and financing the rest at $5\%$ interest for $30$ years. How much money did you pay as your down payment?

$[2]$ How much money was your existing mortgage $($loan$)$ for?

$[3]$ What is your current monthly payment on your existing mortgage? Note: Carry at least $4$ decimal places during calculations, but round your final answer to the nearest cent.

$[4]$ How much total interest will you pay over the life of the existing loan?

$[5]$ This year $(15$ years after you first took out the loan$),$ you check your loan balance. Only part of your payments have been going to pay down the loan; the rest has been going towards interest. You see that you still have $$271,536$ left to pay on your loan. Your house is now valued at $$650,000.$ How much of the original loan have you paid off? $($i$.$e$,$ how much have you reduced the loan balance by$?$

$[6]$ How much money have you paid to the loan company so far $($over the last $15$ years$)?$

$[7]$ How much interest have you paid so far $($over the last $15$ years$)?$

$[8]$ How much equity do you have in your home $($equity is value minus remaining debt$)?$

$[9]$ Since interest rates have dropped, you consider refinancing your mortgage at a lower $3\%$ rate. If you took out a new $30$ year mortgage at$3\%$ for your remaining loan balance, what would your new monthly payments be$?$